二分查找

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数组：【1,2,2,2,3,4,5,6】 二分查找市返回2的位置， 左侧边界和右侧边界的写法：   int binary_search(int[] nums, int target) {     int left = 0, right = nums.length - 1;     while(left <= right) {         int mid = left + (right - left) / 2;         if (nums[mid] < target) {             left = mid + 1;         } else if (nums[mid] > target) {             right = mid - 1;         } else if(nums[mid] == target) {             // 直接返回             return mid;         }     }     // 直接返回     return -1; }   int left_bound(int[] nums, int target) {     int left = 0, right = nums.length - 1;     while (left <= right) {         int mid = left + (right - left) / 2;         if (nums[mid] < target) {             left = mid + 1;         } else if (nums[mid] > target) {             right = mid - 1;         } else if (nums[mid] == target) {             // 别返回，锁定左侧边界             right = mid - 1;         }     }     // 最后要检查 left 越界的情况     if (left >= nums.length || nums[left] != target)         return -1;     return left; }     int right_bound(int[] nums, int target) {     int left = 0, right = nums.length - 1;     while (left <= right) {         int mid = left + (right - left) / 2;         if (nums[mid] < target) {             left = mid + 1;         } else if (nums[mid] > target) {             right = mid - 1;         } else if (nums[mid] == target) {             // 别返回，锁定右侧边界             left = mid + 1;         }     }     // 最后要检查 right 越界的情况     if (right < 0 || nums[right] != target)         return -1;     return right; }