Merge pull request #362 from caitlingao/16_binary_search

feat(geektime_algo): add 16 binary search

rust/16_binary_search/binary_search.rs

@@ -0,0 +1,93 @@
+// 查找第一个给定值的元素
+fn find_first_eq(nums: Vec<i32>, value: i32) -> i32 {
+    if nums.is_empty() { return -1; }
+
+    let mut start = 0;
+    let mut end = nums.len() - 1;
+
+    while start <= end {
+        let mid = start + ((end - start) >> 1);
+        if nums[mid] <= value {
+            if mid == 0 || (nums[mid] == value && nums[mid-1] != value) { return mid as i32; }
+            start = mid + 1;
+        } else {
+            end = mid - 1;
+        }
+    }
+    -1
+}
+
+// 查找最后一个给定值的元素
+fn find_last_eq(nums: Vec<i32>, value: i32) -> i32 {
+    if nums.is_empty() { return -1; }
+
+    let mut start = 0;
+    let mut end = nums.len() - 1;
+
+    while start <= end {
+        let mid = start + ((end - start) >> 1);
+        if nums[mid] <= value {
+            if mid == end || (nums[mid] == value && nums[mid+1] != value) { return mid as i32; }
+            start = mid + 1;
+        } else {
+            end = mid - 1;
+        }
+    }
+    -1
+}
+
+// 查找第一个大于等于给定值的元素
+fn find_first_ge(nums: Vec<i32>, value: i32) -> i32 {
+    if nums.is_empty() { return -1; }
+
+    let mut start = 0;
+    let mut end = nums.len() - 1;
+
+    while start <= end {
+        let mid = start + ((end - start) >> 1);
+        if nums[mid] < value {
+            start = mid + 1;
+        } else {
+            if mid == end || (nums[mid] >= value && nums[mid-1] < value) { return mid as i32; }
+            end = mid - 1;
+        }
+    }
+    -1
+}
+
+// 查找最后一个小于等于给定值的元素
+fn find_last_le(nums: Vec<i32>, value: i32) -> i32 {
+    if nums.is_empty() { return -1; }
+
+    let mut start = 0;
+    let mut end = nums.len() - 1;
+
+    while start <= end {
+        let mid = start + ((end - start) >> 1);
+        if nums[mid] <= value {
+            if mid == 0 || (nums[mid] <= value && nums[mid+1] > value) { return mid as i32; }
+            start = mid + 1;
+        } else {
+            end = mid - 1;
+        }
+    }
+    -1
+}
+
+fn main() {
+    let nums1 = vec![1, 3, 5, 6, 8, 8, 8, 11, 18];
+    let first_eq = find_first_eq(nums1, 8);
+    println!("{:?}", first_eq);
+
+    let nums2 = vec![1, 3, 5, 6, 8, 8, 8, 11, 18];
+    let last_eq = find_last_eq(nums2, 8);
+    println!("{:?}", last_eq);
+
+    let nums3 = vec![1, 3, 5, 6, 8, 8, 8, 11, 18];
+    let find_first_ge = find_first_ge(nums3, 5);
+    println!("{:?}", find_first_ge);
+
+    let nums4 = vec![1, 3, 5, 6, 8, 8, 8, 11, 18];
+    let find_last_le = find_last_le(nums4, 17);
+    println!("{:?}", find_last_le);
+}

rust/16_binary_search/search_in_rotated_sorted_array.rs

@@ -0,0 +1,35 @@
+// leetcode 33 Search in Rotated Sorted Array (https://leetcode.com/problems/search-in-rotated-sorted-array/)
+pub fn search(nums: Vec<i32>, target: i32) -> i32 {
+    if nums.is_empty() { return -1; }
+
+    let mut low = 0;
+    let mut high = nums.len() - 1;
+
+    while low <= high {
+        let mid = low + ((high - low) >> 1);
+        if nums[mid] == target { return mid as i32; }
+
+        // left is order
+        if nums[low] <= nums[mid] {
+            // target is in left array
+            if nums[low] <= target && target <= nums[mid] {
+                high = mid - 1;
+            }  else {
+                low = mid + 1;
+            }
+        } else {
+            if nums[mid] <= target && target <= nums[high] {
+                low = mid + 1;
+            } else {
+                high = mid - 1;
+            }
+        }
+    }
+    -1
+}
+
+fn main() {
+    let nums = vec![4,5,6,7,0,1,2];
+    let n = search(nums, 0);
+    println!("{:?}", n);
+}