34 在排序数组中查找元素的第一个和最后一个位置

https://leetcode.cn/leetbook/read/top-interview-questions-medium/xvpj16/

cost: 9m58s

class Solution {
public:
    vector<int> searchRange(vector<int>& nums, int target) {
        int left = 0, right = nums.size() - 1;
        int start = -1, end = -1;
        while (left <= right) {
            int mid = left + (right - left) / 2;
            int num = nums[mid];
            if (num == target) {
                if (mid == 0 || nums[mid - 1] < target) {
                    start = mid;
                    break;
                } else {
                    right = mid - 1;
                }
            } else if (num < target) {
                left = mid + 1;
            } else if (num > target) {
                right = mid - 1;
            }
        }
        if (start == -1) {
            return {start, end};
        }
        left = start;
        right = nums.size() - 1;
        while (left <= right) {
            int mid = left + (right - left) / 2;
            int num = nums[mid];
            if (num == target) {
                if (mid == nums.size() - 1 || nums[mid + 1] > target) {
                    end = mid;
                    break;
                } else {
                    left = mid + 1;
                }
            } else if (num < target) {
                left = mid + 1;
            } else if (num > target) {
                right = mid - 1;
            }
        }
        return {start, end};
    }
};