Merge pull request #3 from wangzheng0822/master

update

README.md

@@ -1,4 +1,5 @@
 # 数据结构和算法必知必会的50个代码实现
+## (关注“小争哥”公众号，获取我的更多技术、非技术分享)
 
 ## 数组
 * 实现一个支持动态扩容的数组

c-cpp/06_linkedlist/Dlist/Dlist.c

@@ -11,7 +11,7 @@
 
 
 
-void dlist_init(stDlistHead *dlist)
+void dlist_init(stDlistHead *dlist)		//链表初始化
 {
 	dlist->size = 0;
 	dlist->head = NULL;
@@ -19,7 +19,7 @@ void dlist_init(stDlistHead *dlist)
 	return;
 }
 
-void dlist_destory(stDlistHead *dlist)
+void dlist_destory(stDlistHead *dlist)		//删除链表
 {
 	stDlistNode *pNode = NULL;
 	
@@ -36,11 +36,11 @@ void dlist_destory(stDlistHead *dlist)
 	return;
 }
 
-int dlist_insert_head(stDlistHead *dlist,stDlistNode *pNode,int data)
+int dlist_insert_head(stDlistHead *dlist,stDlistNode *pNode,int data)		//插入头结点，操作的链表，操作的节点，数据
 {
-   if(pNode == NULL)
+   if(pNode == NULL)		//当只传递一个数据时
    {
-	    pNode = (stDlistNode *)malloc(sizeof(stDlistNode));
+	    pNode = (stDlistNode *)malloc(sizeof(stDlistNode));		//新建节点，为节点分配空间（malloc（）可能需要#include<malloc.h>）
 	    if (pNode == NULL)
 	    {
 		    return -1;
@@ -51,23 +51,23 @@ int dlist_insert_head(stDlistHead *dlist,stDlistNode *pNode,int data)
 	pNode->prev = NULL;
 	pNode->next = NULL;
 
-	if (dlist->size == 0)
+	if (dlist->size == 0)		//如果链表长度为0，即链表当前无节点，
 	{
 		dlist->head = pNode;
 		dlist->tail = pNode;
 	}
-	else
+	else                           //如果链表已有节点，则令新插入节点为头节点
 	{
 		pNode->next = dlist->head;
 		dlist->head->prev = pNode;
 		dlist->head = pNode;			
 	}
 
-	dlist->size++;
+	dlist->size++;		//每成功调用一次，链表长度+1
 	return 0;
 }
 
-stDlistNode * dlist_remove_tail(stDlistHead *dlist)
+stDlistNode * dlist_remove_tail(stDlistHead *dlist)		//删除尾部节点,并返回删除节点
 {
 	stDlistNode *pNode = NULL;
 
@@ -91,7 +91,7 @@ stDlistNode * dlist_remove_tail(stDlistHead *dlist)
 	return pNode;
 }
 
-void dlist_remove_node(stDlistHead * dlist,stDlistNode *pNode)
+void dlist_remove_node(stDlistHead * dlist,stDlistNode *pNode) 		//删除指定节点
 {
 	if ((dlist == NULL)||(pNode == NULL))
 	{
@@ -119,12 +119,12 @@ void dlist_remove_node(stDlistHead * dlist,stDlistNode *pNode)
 	
 	if (dlist->size == 0)
 	{
-		memset(dlist,0,sizeof(stDlistHead));
+		memset(dlist,0,sizeof(stDlistHead)); 		//将dlist占用内存块的所有值置为0，也就是清空head,tail指针内容
 	}
 
 	return;
 }
-stDlistNode * dlist_search(stDlistHead * dlist,int data)
+stDlistNode * dlist_search(stDlistHead * dlist,int data) 		//根据值搜索节点，并返回
 {
 	stDlistNode *pNode = dlist->head;
 	while(pNode != NULL)
@@ -139,30 +139,30 @@ stDlistNode * dlist_search(stDlistHead * dlist,int data)
 	return NULL;
 }
 
-void dlist_dump(stDlistHead *dlist)
+void dlist_dump(stDlistHead *dlist)		//显示链表中的数据
 {
 	int no = 0;
 	stDlistNode *pNode = dlist->head;
 	while(pNode != NULL)		
 	{
 		printf("\r\n [%d] = %d",no++,pNode->data);
-		pNode = pNode->next;
+		pNode = pNode->next;		//将pNode的下一个节点赋值给pNode，推进循环
 	}
 
 	return;
 }
 
 
-void Lru_dlist(stDlistHead *dlist,int data)
+void Lru_dlist(stDlistHead *dlist,int data) 		//LRU（最近最少使用）缓存淘汰算法
 {
 	stDlistNode *pNode = NULL;
 
 	pNode = dlist_search(dlist,data);		
-	if (pNode != NULL)
+	if (pNode != NULL) 				//如果在链表中找到这个值，则删除储存这个值的节点，之后吧这个节点放在头部
 	{
 		dlist_remove_node(dlist,pNode);
 	}
-	else if(dlist->size >= 4)
+	else if(dlist->size >= 4)			//没在链表中找到，且链表长度大于4，则从链表中删除尾部节点，将新数据放在头部
 	{
 		pNode = dlist_remove_tail(dlist);
 

c-cpp/06_linkedlist/Dlist/Dlist.h

@@ -7,17 +7,17 @@
  ************************************************************************/
 #include<stdio.h>
 
-typedef struct DlistNode
+typedef struct DlistNode          //双向链表中每一个节点
 {				  	
-	struct DlistNode *prev;
+	struct DlistNode *prev;   //节点前项指针
-	struct DlistNode *next;
+	struct DlistNode *next;   //节点后项指针
-	int    data;
+	int    data;              //数据
 }stDlistNode;
 
-typedef struct Dlisthead
+typedef struct Dlisthead          //定义链表总体
 {
-	int size;
+	int size;                 //链表长度
-	stDlistNode *head;
+	stDlistNode *head;        //头指针
-	stDlistNode *tail;
+	stDlistNode *tail;        //尾部指针
 }stDlistHead;
 

c-cpp/24_binarysearchtree/binary_search_tree.cpp

@@ -0,0 +1,268 @@
+#include <iostream>
+
+using namespace std;
+
+typedef int DataType;
+
+struct tree_node
+{
+	DataType data;
+	tree_node* left=NULL;
+	tree_node* right=NULL;
+};
+
+class binary_search_tree{
+private:
+	tree_node* root;
+	int num;
+public:
+	binary_search_tree() :num(0)
+	{
+		root = new tree_node;
+		root->left = NULL;
+		root->right = NULL;
+	}
+
+	bool find(DataType it,tree_node* root)
+	{
+		if (NULL == root)return false;
+		if (it == root->data) {
+			return true;
+		}
+		else if (it > root->data)
+		{
+			return find(it, root->right);
+		}
+		else
+		{
+			return find(it, root->left);
+		}
+	}
+
+	bool find_data(DataType it)
+	{
+		return find(it, root);
+		/*
+		tree_node* p = root;
+		while (p != NULL)
+		{
+			if (it < p->data)p = p->left;
+			else if (it>p->data)p = p->right;
+			else return true;
+		}
+		return false;
+		*/
+	}
+
+
+	void insert_data(DataType it)
+	{
+
+		if (0==num)
+		{
+			root->data = it;
+			num++;
+			return;
+		}
+		tree_node* p = root;
+		while (p != NULL)
+		{
+			if (it < p->data)
+			{
+				if (NULL == p->left)
+				{
+					p->left = new tree_node;
+					p->left->data = it;
+					num++;
+					return;
+				}
+				p = p->left;
+			}
+			else
+			{
+				if (NULL == p->right)
+				{
+					p->right = new tree_node;
+					p->right->data = it;
+					num++;
+					return;
+				}
+				p = p->right;
+			}
+		}
+		
+	}
+
+	void delet(DataType it)
+	{
+		if (NULL == root)return;
+		tree_node* p = root;
+		tree_node* pp = NULL;//pp记录的是p的父节点
+		while (p != NULL&&p->data != it)
+		{
+			pp = p;
+			if (it > p->data)p = p->right;
+			else
+				p = p->left;
+		}
+		if (p == NULL)return;//没有找到
+		//删除的节点有两个子节点
+		if (p->left != NULL&&p->right != NULL)
+		{
+			tree_node* minP = p->right;
+			tree_node* minPP = p;//记录P的父节点
+			while (minP->left != NULL)//寻找右子树最小节点
+			{
+				minPP = minP;
+				minP = minP->left;
+			}
+			p->data = minP->data;//将minP替换到p中
+			//将p换到叶节点上，使用叶节点方法进行删除
+			p = minP;
+			pp = minPP;
+		}
+
+		//删除节点是叶节点或者是仅有一个节点
+		tree_node* child;
+		if (p->left != NULL) child = p->left;
+		else if (p->right != NULL) child = p->right;
+		else child = NULL;
+
+		if (NULL == pp) root = child;//删除的是根节点
+		else if (p == pp->left)pp->left = child;
+		else pp->right = child;
+	}
+
+	DataType get_max()
+	{
+		if (NULL == root)return NULL;
+		tree_node* tmp=root;
+		while (tmp->right != NULL)
+		{
+			tmp = tmp->right;
+		}
+		return tmp->data;
+	}
+	DataType get_min()
+	{
+		if (NULL == root)return NULL;
+		tree_node* tmp=root;
+		while (tmp->left != NULL)
+		{
+			tmp = tmp->left;
+		}
+		return tmp->data;
+	}
+
+	DataType get_prenode(DataType it)
+	{
+		if (NULL == root)return NULL;
+		if (it == root->data) return NULL;
+		tree_node* p=root;
+		tree_node* pp=NULL;
+		while ((p->data != it)&&(p!=NULL))
+		{
+			pp = p;
+			if (p->data < it)
+			{
+				p=p->right;
+			}
+			else
+			{
+				p = p->left;
+			}
+		}
+		return ((NULL==p)?NULL:pp->data);
+	}
+
+	DataType get_postnode(DataType it)
+	{
+		if (NULL == root)return -1;
+		tree_node* p = root;
+		while ((p->data != it) && (p != NULL))
+		{
+			if (p->data < it)
+			{
+				p = p->left;
+			}
+			else
+			{
+				p = p->right;
+			}
+		}
+		if (NULL == p)
+		{
+			return -1;
+		}
+		else if (p->left!=NULL)
+		{
+			return p->left->data;
+		}
+		else if (p->right!=-NULL)
+		{
+			return p->right->data;
+		}
+		else
+		{
+			return NULL;
+		}
+	}
+
+	void mid_order(tree_node* rt)
+	{
+		if (NULL == rt)return;
+		mid_order(rt->left);
+		cout << rt->data;
+		mid_order(rt->right);
+	}
+	void order()
+	{
+		if (NULL == root)return;
+		return mid_order(root);
+	}
+
+	int get_high(tree_node* rt)
+	{
+		int lhigh = 0;
+		int rhigh = 0;
+		if (NULL == rt)return 0;
+		lhigh = get_high(rt->left);
+		rhigh = get_high(rt->right);
+		return ((lhigh > rhigh) ? (lhigh + 1) : (rhigh + 1));
+	}
+
+	int high()
+	{
+		if (NULL == root) return 1;
+		return get_high(root);
+	}
+};
+
+int main()
+{
+	binary_search_tree my_tree;
+
+	my_tree.insert_data(5);
+	my_tree.insert_data(4);
+	my_tree.insert_data(6);
+	my_tree.insert_data(10);
+	my_tree.insert_data(3);
+	my_tree.insert_data(8);
+	my_tree.insert_data(1);
+	if (my_tree.find_data(3))
+	{
+		cout << "找到了数字3" << endl;
+	}
+	else
+	{
+		cout << "没有找到数字3" << endl;
+	}
+	my_tree.delet(4);
+	cout << "Max" << my_tree.get_max() << endl;
+	cout << "Min" << my_tree.get_min() << endl;
+	cout << "pre node of 5 is " <<my_tree.get_prenode(5) <<endl;
+	cout << "post node of 5 is " << my_tree.get_postnode(5) << endl;
+	my_tree.order();
+	cout << "high of tree is " << my_tree.high() << endl;
+	return 0;
+} 

go/20_lru/lru_cache.go

@@ -0,0 +1,148 @@
+package lru_cache
+
+const (
+	hostbit = uint64(^uint(0)) == ^uint64(0)
+	LENGTH  = 100
+)
+
+type lruNode struct {
+	prev *lruNode
+	next *lruNode
+
+	key   int // lru key
+	value int // lru value
+
+	hnext *lruNode // 拉链
+}
+
+type LRUCache struct {
+	node []lruNode // hash list
+
+	head *lruNode // lru head node
+	tail *lruNode // lru tail node
+
+	capacity int //
+	used     int //
+}
+
+func Constructor(capacity int) LRUCache {
+	return LRUCache{
+		node:     make([]lruNode, LENGTH),
+		head:     nil,
+		tail:     nil,
+		capacity: capacity,
+		used:     0,
+	}
+}
+
+func (this *LRUCache) Get(key int) int {
+	if this.tail == nil {
+		return -1
+	}
+
+	if tmp := this.searchNode(key); tmp != nil {
+		this.moveToTail(tmp)
+		return tmp.value
+	}
+	return -1
+}
+
+func (this *LRUCache) Put(key int, value int) {
+	// 1. 首次插入数据
+	// 2. 插入数据不在 LRU 中
+	// 3. 插入数据在 LRU 中
+	// 4. 插入数据不在 LRU 中, 并且 LRU 已满
+
+	if tmp := this.searchNode(key); tmp != nil {
+		tmp.value = value
+		this.moveToTail(tmp)
+		return
+	}
+	this.addNode(key, value)
+
+	if this.used > this.capacity {
+		this.delNode()
+	}
+}
+
+func (this *LRUCache) addNode(key int, value int) {
+	newNode := &lruNode{
+		key:   key,
+		value: value,
+	}
+
+	tmp := &this.node[hash(key)]
+	newNode.hnext = tmp.hnext
+	tmp.hnext = newNode
+	this.used++
+
+	if this.tail == nil {
+		this.tail, this.head = newNode, newNode
+		return
+	}
+	this.tail.next = newNode
+	newNode.prev = this.tail
+	this.tail = newNode
+}
+
+func (this *LRUCache) delNode() {
+	if this.head == nil {
+		return
+	}
+	prev := &this.node[hash(this.head.key)]
+	tmp := prev.hnext
+
+	for tmp != nil && tmp.key != this.head.key {
+		prev = tmp
+		tmp = tmp.hnext
+	}
+	if tmp == nil {
+		return
+	}
+	prev.hnext = tmp.hnext
+	this.head = this.head.next
+	this.head.prev = nil
+	this.used--
+}
+
+func (this *LRUCache) searchNode(key int) *lruNode {
+	if this.tail == nil {
+		return nil
+	}
+
+	// 查找
+	tmp := this.node[hash(key)].hnext
+	for tmp != nil {
+		if tmp.key == key {
+			return tmp
+		}
+		tmp = tmp.hnext
+	}
+	return nil
+}
+
+func (this *LRUCache) moveToTail(node *lruNode) {
+	if this.tail == node {
+		return
+	}
+	if this.head == node {
+		this.head = node.next
+		this.head.prev = nil
+	} else {
+		node.next.prev = node.prev
+		node.prev.next = node.next
+	}
+
+	node.next = nil
+	this.tail.next = node
+	node.prev = this.tail
+
+	this.tail = node
+}
+
+func hash(key int) int {
+	if hostbit {
+		return (key ^ (key >> 32)) & (LENGTH - 1)
+	}
+	return (key ^ (key >> 16)) & (LENGTH - 1)
+}

go/20_lru/lru_cache_test.go

@@ -0,0 +1,67 @@
+package lru_cache
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_Hostbit(t *testing.T) {
+	fmt.Println(hostbit)
+}
+
+func Test_LRU(t *testing.T) {
+	lru := Constructor(2)
+
+	lru.Put(1, 1)
+	lru.Put(2, 2)
+	assert.Equal(t, lru.Get(1), 1)  // returns 1
+	lru.Put(3, 3)                   // evicts key 2
+	assert.Equal(t, lru.Get(2), -1) // returns -1 (not found)
+	lru.Put(4, 4)                   // evicts key 1
+	assert.Equal(t, lru.Get(1), -1) // returns -1 (not found)
+	assert.Equal(t, lru.Get(3), 3)  // returns 3
+	assert.Equal(t, lru.Get(4), 4)  // returns 4
+}
+
+func Test_LRU_PutGet(t *testing.T) {
+	lru := Constructor(1)
+
+	lru.Put(1, 2)
+	assert.Equal(t, lru.Get(1), 2) // returns 2
+}
+
+func Test_LRU_PutGetPutGetGet(t *testing.T) {
+	lru := Constructor(1)
+
+	lru.Put(2, 1)
+	assert.Equal(t, lru.Get(2), 1) // returns 1
+	lru.Put(3, 2)
+	assert.Equal(t, lru.Get(2), -1) // returns -1
+	assert.Equal(t, lru.Get(3), 2)  // returns 2
+}
+
+func Test_LRU_PPGPPG(t *testing.T) {
+	lru := Constructor(2)
+
+	lru.Put(2, 1)
+	lru.Put(2, 2)
+	assert.Equal(t, lru.Get(2), 2) // returns 2
+	lru.Put(1, 4)
+	lru.Put(4, 1)
+	assert.Equal(t, lru.Get(2), -1) // returns -1
+	assert.Equal(t, lru.Get(3), -1) // returns -1
+}
+
+func Test_LRU_PPGPPG_2(t *testing.T) {
+	lru := Constructor(2)
+
+	lru.Put(2, 1)
+	lru.Put(2, 2)
+	assert.Equal(t, lru.Get(2), 2) // returns 2
+	lru.Put(1, 1)
+	lru.Put(4, 1)
+	assert.Equal(t, lru.Get(2), -1) // returns -1
+	assert.Equal(t, lru.Get(3), -1) // returns -1
+}

java/12_sorts/KthSmallest.java

@@ -0,0 +1,51 @@
+package sort;
+
+/**
+ * @author wangjunwei87
+ * @since 2019-03-10
+ */
+public class KthSmallest {
+
+    public static int kthSmallest(int[] arr, int k) {
+        if (arr == null || arr.length < k) {
+            return -1;
+        }
+
+        int partition = partition(arr, 0, arr.length - 1);
+        while (partition + 1 != k) {
+            if (partition + 1 < k) {
+                partition = partition(arr, partition + 1, arr.length - 1);
+            } else {
+                partition = partition(arr, 0, partition - 1);
+            }
+        }
+
+        return arr[partition];
+    }
+
+    private static int partition(int[] arr, int p, int r) {
+        int pivot = arr[r];
+
+        int i = p;
+        for (int j = p; j <= r - 1; j++) {
+            if (arr[j] < pivot) {
+                swap(arr, i, j);
+                i++;
+            }
+        }
+
+        swap(arr, i, r);
+
+        return i;
+    }
+
+    private static void swap(int[] arr, int i, int j) {
+        if (i == j) {
+            return;
+        }
+
+        int tmp = arr[i];
+        arr[i] = arr[j];
+        arr[j] = tmp;
+    }
+}

javascript/42_dynamic_programming/levenshtein_distance.js

@@ -0,0 +1,54 @@
+function lsDist(str1, str2) {
+    var n = str1.length;
+    var m = str2.length;
+
+    var memo = new Array(n);
+    for(let i = 0; i < n; i++) {
+        memo[i] = new Array(m);
+        if (str1[i] === str2[0]) {
+            memo[i][0] = i - 0;
+        } else if(i === 0) {
+            memo[i][0] = 1;
+        } else {
+            memo[i][0] = memo[i - 1][0] + 1;
+        }
+    }
+
+    for(let j = 0; j < m; j++) {
+        if(str1[0] === str2[j]) {
+            memo[0][j] = j - 0;
+        } else if(j === 0) {
+            memo[0][j] = 1;
+        } else {
+            memo[0][j] = memo[0][j - 1] + 1;
+        }
+    }
+
+    for(let i = 1; i < n; i++) {
+        for(let j = 1; j < m; j++) {
+            if(str1[i] === str2[j]) {
+                memo[i][j] = Math.min(memo[i - 1][j] + 1, memo[i][j - 1] + 1, memo[i - 1][j - 1 ]);
+            } else {
+                memo[i][j] = Math.min(memo[i - 1][j] + 1, memo[i][j - 1] + 1, memo[i - 1][j - 1 ] + 1);
+            }
+        }
+    }
+    console.log(memo);
+
+    return memo[n - 1][m - 1];
+}
+
+
+var s = "mitcmu";
+var t = "mtacnu";
+
+console.log( lsDist(s, t) );
+
+var s = "kitten";
+var t = "sitting";
+
+console.log( lsDist(s, t) );
+
+var s = "flaw";
+var t = "lawn";
+console.log( lsDist(s, t) );

php/15_binary/binary.php

@@ -86,7 +86,11 @@ function squareRoot($number)
 function getDecimalPlaces($number)
 {
     $temp = explode('.', $number);
-    return strlen($temp[1]);
+    if (isset($temp[1])) {
+        return strlen($temp[1]);
+    }
+
+    return 0;
 }
 
 // 测试二分查找给定值

php/24_tree/Tree.php

@@ -0,0 +1,152 @@
+<?php
+
+namespace Algo_24;
+
+class Tree
+{
+
+    /**
+     * 树的根节点
+     * @var [type]
+     */
+    public $head = null;
+
+    /**
+     * [__construct description]
+     * @param TreeNode|null $head [description]
+     */
+    public function __construct($headData = null)
+    {
+        if ($headData != null) {
+            $this->head = new TreeNode($headData);
+        }
+    }
+
+    /**
+     * 查找数据
+     * @param  [type] $data [数据]
+     * @return [type]       [description]
+     */
+    public function find($data)
+    {
+        if ($this->head == null) {
+            return null;
+        }
+
+        $node = $this->head;
+
+        while ($node != null) {
+            if ($node->data == $data) {
+                return $node;
+            } elseif ($data > $node->data) {
+                $node = $node->right;
+            } else {
+                $node = $node->left;
+            }
+        }
+
+        return null;
+    }
+
+    /**
+     * 插入数据
+     * @param  [type] $data [数据]
+     * @return [type]       [description]
+     */
+    public function insert($data)
+    {
+        if ($this->head == null) {
+            $this->head = new TreeNode($data);
+            return true;
+        }
+
+        $node = $this->head;
+
+        while ($node != null) {
+            if ($data > $node->data) {
+                if ($node->right == null) {
+                    $node->right = new TreeNode($data);
+                    return true;
+                }
+                $node = $node->right;
+            } else {
+                if ($node->left == null) {
+                    $node->left = new TreeNode($data);
+                    return true;
+                }
+                $node = $node->left;
+            }
+        }
+    }
+
+    /**
+     * 删除节点
+     * @param  [type] $data [节点]
+     * @return [type]       [description]
+     */
+    public function delete($data)
+    {
+        // 找到需要删除节点
+        $node = $this->head;
+        $pnode = null;
+        while ($node != null) {
+            if ($node->data == $data) {
+                break;
+            } elseif ($data > $node->data) {
+                $pnode = $node;
+                $node = $node->right;
+            } else {
+                $pnode = $node;
+                $node = $node->left;
+            }
+        }        
+        if ($node == null) {
+            return false;
+        }
+        // 要删除的节点有两个子节点
+        // 查找右子树中最小节点
+        if ($node->left != null && $node->right != null) {
+            $minPP = $node;
+            $minP = $node->right;
+            while ($minP->left != null) {
+                $minPP = $minP;
+                $minP = $minP->left;
+            }
+            $node->data = $minP->data;
+            $node = $minP;
+            // 删除掉右子树中的最小节点
+            $minPP->left = null;
+        }
+
+        if ($node->left != null) {
+            $child = $node->left;
+        } elseif ($node->right != null) {
+            $child = $node->right;
+        } else {
+            $child = null;
+        }
+
+        if ($pnode == null) {
+            // 删除的是根节点
+            $node = $child;
+        } elseif ($pnode->left == $node) {
+            $pnode->left = $child;
+        } else {
+            $pnode->right = $child;
+        }
+    }
+
+    /**
+     * 前序遍历
+     * @return [type] [description]
+     */
+    public function preOrder($node)
+    {
+        if ($node == null) {
+            return ;            
+        }
+        echo $node->data . '->';
+        $this->preOrder($node->left);
+        $this->preOrder($node->right);
+    }
+}

php/24_tree/TreeNode.php

@@ -0,0 +1,36 @@
+<?php
+
+namespace Algo_24;
+
+class TreeNode
+{
+
+    /**
+     * 节点中的数据
+     * @var [type]
+     */
+    public $data;
+
+    /**
+     * 左节点
+     * @var [type]
+     */
+    public $left;
+
+    /**
+     * 右节点
+     * @var [type]
+     */
+    public $right;
+
+    /**
+     * [__construct description]
+     * @param [type] $data [description]
+     */
+    public function __construct($data = null)
+    {
+        $this->data = $data;
+        $this->left = null;
+        $this->right = null;
+    }
+}

php/24_tree/main.php

@@ -0,0 +1,25 @@
+<?php
+
+namespace Algo_24;
+
+require_once '../vendor/autoload.php';
+
+
+$tree = new Tree();
+
+$tree->insert(20);
+$tree->insert(30);
+$tree->insert(10);
+$tree->insert(21);
+$tree->insert(22);
+
+$tree->preOrder($tree->head);
+echo PHP_EOL;
+
+var_dump($tree->find(30));
+echo PHP_EOL;
+
+
+$tree->delete(30);
+$tree->preOrder($tree->head);
+echo PHP_EOL;

php/composer.json

@@ -8,7 +8,8 @@
             "Algo_06\\": "06_linkedlist/",
             "Algo_07\\": "07_linkedlist/",
             "Algo_08\\": "08_stack/",
-            "Algo_09\\": "09_queue/"
+            "Algo_09\\": "09_queue/",
+            "Algo_24\\": "24_tree/"
         }
     }
 }

python/06_linkedlist/singly_linked_list.py

@@ -83,7 +83,7 @@ class SinglyLinkedList:
             current = current._next
         if not current:  # node not in the list
             return
-        current._next = None
+        current._next = node._next
 
     def delete_by_value(self, value: int):
         if not self._head or not value:

python/09_queue/array_queue.py

@@ -21,11 +21,7 @@ class ArrayQueue:
                 return False
             else:
                 for i in range(0, self._tail - self._head):
-<<<<<<< HEAD
-                    self._data[i] = self._items[i + self._head]
-=======
                     self._items[i] = self._items[i + self._head]
->>>>>>> upstream/master
                 self._tail = self._tail - self._head
                 self._head = 0
         
@@ -38,6 +34,8 @@ class ArrayQueue:
             item = self._items[self._head]
             self._head += 1
             return item
+        else:
+            return None
     
     def __repr__(self) -> str:
         return " ".join(item for item in self._items[self._head : self._tail])

python/15_bsearch/bsearch_recursion.py

@@ -0,0 +1,22 @@
+"""
+    Author: dreamkong
+"""
+
+from typing import List
+
+
+def bsearch(nums: List[int], target: int) -> int:
+    return bsearch_internally(nums, 0, len(nums)-1, target)
+
+
+def bsearch_internally(nums: List[int], low: int, high: int, target: int) -> int:
+    if low > high:
+        return -1
+
+    mid = low+int((high-low) >> 2)
+    if nums[mid] == target:
+        return mid
+    elif nums[mid] < target:
+        return bsearch_internally(nums, mid+1, high, target)
+    else:
+        return bsearch_internally(nums, low, mid-1, target)

python/42_dynamic_programming/min_edit_dist.py

@@ -4,13 +4,29 @@
 
 def levenshtein_dp(s: str, t: str) -> int:
     m, n = len(s), len(t)
-    table = [[0] * (n + 1) for _ in range(m + 1)]
+    table = [[0] * (n) for _ in range(m)]
-    table[0] = [j for j in range(m + 1)]
+
-    for i in range(m + 1):
+    for i in range(n):
-        table[i][0] = i
+        if s[0] == t[i]:
-    for i in range(1, m + 1):
+            table[0][i] = i - 0
-        for j in range(1, n + 1):
+        elif i != 0:
-            table[i][j] = min(1 + table[i - 1][j], 1 + table[i][j - 1], int(s[i - 1] != t[j - 1]) + table[i - 1][j - 1])
+            table[0][i] = table[0][i - 1] + 1
+        else:
+            table[0][i] = 1
+
+    for i in range(m):
+        if s[i] == t[0]:
+            table[i][0] = i - 0
+        elif i != 0:
+            table[i][0] = table[i - 1][0] + 1
+        else:
+            table[i][0] = 1
+
+    for i in range(1, m):
+        for j in range(1, n):
+            table[i][j] = min(1 + table[i - 1][j], 1 + table[i][j - 1], int(s[i] != t[j]) + table[i - 1][j - 1])
+
+    print(table)
     return table[-1][-1]
 
 
@@ -29,3 +45,15 @@ if __name__ == "__main__":
 
     print(levenshtein_dp(s, t))
     print(common_substring_dp(s, t))
+
+    s = "kitten"
+    t = "sitting"
+
+    print(levenshtein_dp(s, t))
+    print(common_substring_dp(s, t))
+
+    s = "flaw"
+    t = "lawn"
+
+    print(levenshtein_dp(s, t))
+    print(common_substring_dp(s, t))

swift/08_stack/StackBasedOnLinkedList.swift

@@ -14,8 +14,10 @@ struct StackBasedOnLinkedList<Element>: Stack {
     
     var size: Int {
         var count = 0
-        while head.next != nil {
+        var cur = head.next
+        while cur != nil {
             count += 1
+            cur = cur?.next
         }
         return count
     }