代码实现：

思路：二分法

方法一：分别查找左右侧边界

/*** Note: The returned array must be malloced, assume caller calls free().*/
int GetTargetFirstPosition(int *nums, int numsSize, int target) {int l = 0, r = numsSize - 1;while (l <= r) {int mid = (l + r) >> 1;/* 找到 target，缩小搜索区间的上界 r ，不断向左收缩锁定左侧边界 */if (nums[mid] == target) {/* 在区间 [l, mid - 1] 中查找 */r = mid - 1;} else if (nums[mid] > target) {r = mid - 1;} else if (nums[mid] < target) {l = mid + 1;}}if (l == numsSize || nums[l] != target) {return -1;}return l;
}int GetTargetLastPosition(int *nums, int numsSize, int target) {int l = 0, r = numsSize - 1;while (l <= r) {int mid = (l + r) >> 1;if (nums[mid] == target) {l = mid + 1;} else if (nums[mid] > target) {r = mid - 1;} else if (nums[mid] < target) {l = mid + 1;   }}if (r == -1 || nums[r] != target) {return -1;}return r;
}int* searchRange(int *nums, int numsSize, int target, int *returnSize) {int *res = malloc(sizeof(int) * 2);memset(res, -1, sizeof(res));*returnSize = 2;if (nums == NULL || numsSize < 1) {return res;}int firstPos = GetTargetFirstPosition(nums, numsSize, target);// 左边界没找到，右边界肯定也找不到if (firstPos == -1) {return res;}res[0] = firstPos;int lastPos = GetTargetLastPosition(nums, numsSize, target);res[1] = lastPos;return res;    
}

方法二：一次查找

/*** Note: The returned array must be malloced, assume caller calls free().*/int binarySearch(int *nums, int numsSize, int target) {int l = 0, r = numsSize - 1;         while (l <= r) {            int mid = (l + r) >> 1;  if (nums[mid] == target) {            return mid;} else if (nums[mid] > target) {      r = mid - 1;} else if (nums[mid] < target) {      l = mid + 1;}}return -1;
}int* searchRange(int *nums, int numsSize, int target, int *returnSize) {int *res = malloc(sizeof(int) * 2);memset(res, -1, sizeof(int) * 2);*returnSize = 2;if (nums == NULL || numsSize < 1) {return res;}int ind = binarySearch(nums, numsSize, target);if (ind == -1) {return res;}int i, j;for (i = ind - 1; i >= 0; i--) {if (nums[i] != target) {break;}}res[0] = i + 1;for (j = ind + 1; j < numsSize; j++) {if (nums[j] != target) {break;}}res[1] = --j;return res;
}