2023每日刷题（六）

Leetcode—34.在排序数组中查找元素的第一个和最后一个位置

实现代码

/**
 * Note: The returned array must be malloced, assume caller calls free().
 */
int lower_bound(int *arr, int numsSize, int target) {
    // 左闭右开区间[left, target)
    int left = 0, right = numsSize;
    int mid;
    while(left < right) {
        mid = left + (right - left) / 2;
        if(arr[mid] < target) {
            left = mid + 1;
        } else {
            right = mid;
        }
    }
    return left;
}


int* searchRange(int* nums, int numsSize, int target, int* returnSize){
    int *ans = (int *)malloc(sizeof(int) * 2);
    *returnSize = 2;
    ans[0] = -1;
    ans[1] = -1;
    int left = lower_bound(nums, numsSize, target);
    int right = lower_bound(nums, numsSize, target + 1) - 1;
    if(numsSize != 0 && left != numsSize && nums[left] == target) {
        ans[0] = left;
        ans[1] = right;
    } 
    return ans;
}

运行结果

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