添加leetcode 124 105题关于二叉树部分内容

.gitignore

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+out/

.vscode/launch.json

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+{
+    // 使用 IntelliSense 了解相关属性。 
+    // 悬停以查看现有属性的描述。
+    // 欲了解更多信息，请访问: https://go.microsoft.com/fwlink/?linkid=830387
+    "version": "0.2.0",
+    "configurations": [
+        {
+            "name": "(gdb) Launch",
+            "type": "cppdbg",
+            "request": "launch",
+            "program": "${workspaceRoot}/out/${fileBasenameNoExtension}",
+            // 此处若可执行文件不想放在一个文件夹中，则把 /out 删去即可
+            "args": [],
+            "stopAtEntry": false,
+            "cwd": "${workspaceRoot}",
+            // 此处${workspaceRoot}与${workspaceFolder}应该类似，但网上资料大部分用的前者
+            "environment": [],
+            "externalConsole": false,
+            "MIMode": "gdb",
+            "setupCommands": [
+                {
+                    "description": "Enable pretty-printing for gdb",
+                    "text": "-enable-pretty-printing",
+                    "ignoreFailures": true
+                }
+            ],
+            "preLaunchTask": "C/C++: g++ build active file",
+            // 此处要与tasks.json中的label相同
+            "miDebuggerPath": "/usr/bin/gdb"
+        }
+    ]
+}

.vscode/settings.json

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+{
+    "files.associations": {
+        "iostream": "cpp",
+        "ostream": "cpp",
+        "any": "cpp",
+        "array": "cpp",
+        "atomic": "cpp",
+        "bit": "cpp",
+        "*.tcc": "cpp",
+        "bitset": "cpp",
+        "cctype": "cpp",
+        "cfenv": "cpp",
+        "charconv": "cpp",
+        "chrono": "cpp",
+        "cinttypes": "cpp",
+        "clocale": "cpp",
+        "cmath": "cpp",
+        "codecvt": "cpp",
+        "compare": "cpp",
+        "complex": "cpp",
+        "concepts": "cpp",
+        "condition_variable": "cpp",
+        "coroutine": "cpp",
+        "csetjmp": "cpp",
+        "csignal": "cpp",
+        "cstdarg": "cpp",
+        "cstddef": "cpp",
+        "cstdint": "cpp",
+        "cstdio": "cpp",
+        "cstdlib": "cpp",
+        "cstring": "cpp",
+        "ctime": "cpp",
+        "cuchar": "cpp",
+        "cwchar": "cpp",
+        "cwctype": "cpp",
+        "deque": "cpp",
+        "forward_list": "cpp",
+        "list": "cpp",
+        "map": "cpp",
+        "set": "cpp",
+        "unordered_map": "cpp",
+        "unordered_set": "cpp",
+        "vector": "cpp",
+        "exception": "cpp",
+        "algorithm": "cpp",
+        "functional": "cpp",
+        "iterator": "cpp",
+        "memory": "cpp",
+        "memory_resource": "cpp",
+        "numeric": "cpp",
+        "optional": "cpp",
+        "random": "cpp",
+        "ratio": "cpp",
+        "regex": "cpp",
+        "source_location": "cpp",
+        "string": "cpp",
+        "string_view": "cpp",
+        "system_error": "cpp",
+        "tuple": "cpp",
+        "type_traits": "cpp",
+        "utility": "cpp",
+        "fstream": "cpp",
+        "future": "cpp",
+        "initializer_list": "cpp",
+        "iomanip": "cpp",
+        "iosfwd": "cpp",
+        "istream": "cpp",
+        "limits": "cpp",
+        "mutex": "cpp",
+        "new": "cpp",
+        "numbers": "cpp",
+        "ranges": "cpp",
+        "scoped_allocator": "cpp",
+        "shared_mutex": "cpp",
+        "span": "cpp",
+        "sstream": "cpp",
+        "stdexcept": "cpp",
+        "stop_token": "cpp",
+        "streambuf": "cpp",
+        "thread": "cpp",
+        "typeindex": "cpp",
+        "typeinfo": "cpp",
+        "valarray": "cpp",
+        "variant": "cpp",
+        "barrier": "cpp",
+        "latch": "cpp",
+        "semaphore": "cpp",
+        "syncstream": "cpp"
+    }
+}

.vscode/tasks.json

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+{
+    "tasks": [
+        {
+            "type": "shell",
+            // 此处type的属性问题下面详说
+            "label": "C/C++: g++ build active file",
+            "command": "/usr/bin/g++",
+            "presentation": {
+                "echo": true,
+                "reveal": "always",
+                "focus": false,
+                "panel": "shared",
+                "showReuseMessage": true,
+                "clear": false
+            },
+            "args": [
+                "-g",
+                "${file}",
+                "-std=c++17",
+                "-o",
+                "${workspaceRoot}/out/${fileBasenameNoExtension}"
+            ],
+            // 此处与launch.json中类似，若不需要则删去 /out
+            "options": {
+                "cwd": "${workspaceFolder}"
+            },
+            "problemMatcher": [
+                "$gcc"
+            ],
+            "group": {
+                "kind": "build",
+                "isDefault": true
+            },
+            "detail": "Task generated by Debugger."
+        }
+    ],
+    "version": "2.0.0"
+}

tree/Binary_tree/leetcode_105/main.cpp

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+/*
+ * @Description:
+ * @Version: 1.0
+ * @Autor: zhuyijun
+ * @Date: 2021-11-10 13:09:52
+ * @LastEditTime: 2021-11-10 16:39:11
+ */
+/*
+    题目: 给定一棵树的前序遍历 preorder 与中序遍历
+    inorder。请构造二叉树并返回其根节点。
+
+    Input: preorder = [3,9,20,15,7], inorder = [9,3,15,20,7]
+    Output: [3,9,20,null,null,15,7]
+
+    示例 2:
+    Input: preorder = [-1], inorder = [-1]
+    Output: [-1]
+
+    提示:
+    1 <= preorder.length <= 3000
+    inorder.length == preorder.length
+    -3000 <= preorder[i], inorder[i] <= 3000
+    preorder 和 inorder 均无重复元素
+    inorder 均出现在 preorder
+    preorder 保证为二叉树的前序遍历序列
+    inorder 保证为二叉树的中序遍历序列
+ */
+
+// 前序:root -> left -> right  中序 left->root->right   后序: right->left->root
+#include <bits/stdc++.h>
+using namespace std;
+struct TreeNode {
+  int val;
+  TreeNode *left;
+  TreeNode *right;
+  TreeNode() : val(0), left(nullptr), right(nullptr) {}
+  TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+  TreeNode(int x, TreeNode *left, TreeNode *right)
+      : val(x), left(left), right(right) {}
+};
+
+TreeNode *pre_order(vector<int> &pre, int leftpre, int rightpre,
+                    vector<int> &in, int leftin, int rightin) {
+  if (leftpre > rightpre || leftin > rightin) return nullptr;
+
+  TreeNode *root = new TreeNode(pre[leftpre]);
+
+  int rootin = leftin;
+
+  while (rootin <= rightin && in[rootin] != pre[leftpre]) rootin++;
+  int left = rootin - leftin;
+
+  root->left =
+      pre_order(pre, leftpre + 1, leftpre + left, in, leftin, rootin - 1);
+
+  root->right =
+      pre_order(pre, leftpre + left + 1, rightpre, in, rootin + 1, rightin);
+  return root;
+}
+
+TreeNode *buildTree(vector<int> &preorder, vector<int> &inorder) {
+  return pre_order(preorder, 0, preorder.size() - 1, inorder, 0,
+                   inorder.size() - 1);
+}
+
+void printTree(TreeNode *root, vector<int> *res) {
+  if (root == nullptr) {
+    return;
+  }
+  res->push_back(root->val);
+  printTree(root->left, res);
+  printTree(root->right, res);
+}
+int main() {
+  vector<int> pre;
+  pre.push_back(3);
+  pre.push_back(9);
+  pre.push_back(20);
+  pre.push_back(15);
+  pre.push_back(7);
+
+  vector<int> in;
+  in.push_back(9);
+  in.push_back(3);
+  in.push_back(15);
+  in.push_back(20);
+  in.push_back(7);
+  TreeNode *root = buildTree(pre, in);
+  vector<int> res;
+  printTree(root, &res);
+  for (int i = 0; i < res.size(); i++) {
+    std::cout << res[i] << " ";
+  }
+  return 0;
+}

tree/Binary_tree/leetcode_124/main.cpp

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+/*
+ * @Description:
+ * @Version: 1.0
+ * @Autor: zhuyijun
+ * @Date: 2021-11-10 09:09:12
+ * @LastEditTime: 2021-11-10 13:21:51
+ */
+// 路径
+// 被定义为一条从树中任意节点出发，沿父节点-子节点连接，达到任意节点的序列。
+//同一个节点在一条路径序列中 至多出现一次 。该路径 至少包含一个
+//节点，且不一定经过根节点。
+// 路径和 是路径中各节点值的总和。
+
+// 给你一个二叉树的根节点 root ，返回其 最大路径和 。
+
+//  
+
+// 示例 1：
+
+// 输入：root = [1,2,3]
+// 输出：6
+// 解释：最优路径是 2 -> 1 -> 3 ，路径和为 2 + 1 + 3 = 6
+// 示例 2：
+
+// 输入：root = [-10,9,20,null,null,15,7]
+// 输出：42
+// 解释：最优路径是 15 -> 20 -> 7 ，路径和为 15 + 20 + 7 = 42
+//  
+
+// 提示：
+
+// 树中节点数目范围是 [1, 3 * 104]
+// -1000 <= Node.val <= 1000
+
+#include <bits/stdc++.h>
+using namespace std;
+struct TreeNode {
+  int val;
+  TreeNode *left;
+  TreeNode *right;
+  TreeNode() : val(0), left(nullptr), right(nullptr) {}
+  TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+  TreeNode(int x, TreeNode *left, TreeNode *right)
+      : val(x), left(left), right(right) {}
+};
+
+int maxPathSum(TreeNode *root, int &val) {
+  if (root == nullptr) return 0;
+  int left = maxPathSum(root->left, val);
+  int right = maxPathSum(root->right, val);
+  int lmr = root->val + max(0, left) + max(0, right);
+  int ret = root->val + max(0, max(left, right));
+  val = max(val, max(lmr, ret));
+  return ret;
+}
+
+int maxPathSum(TreeNode *root) {
+  int val = INT_MIN;
+  maxPathSum(root, val);
+  return val;
+}
+
+int main() {
+  TreeNode root = TreeNode();
+  std::cout << maxPathSum(&root);
+}