数字在排序数组中出现的次数

统计一个数字在排序数组中出现的次数。

 

示例 1:

输入: nums = [5,7,7,8,8,10], target = 8
输出: 2
示例 2:

输入: nums = [5,7,7,8,8,10], target = 6
输出: 0
 

限制：

0 <= 数组长度 <= 50000

class Solution {
public:
    int search(vector<int>& nums, int target) {
        if(nums.empty()) {
            return 0;
        }

        int left = 0;
        int right = nums.size() - 1;
        //二分查找，left为左边第一个和target相等的数字下标
        while(left < right) {
            int mid = left + (right - left) / 2;
            if(target <= nums[mid]) {
                right = mid;
            }
            if(target > nums[mid]) {
                left = mid + 1;
            }
        }
        int max_right = nums.size();
        for(int i = left; i < max_right; ++i) {
            if(target == nums[i]) {
                ++right;
            }
        }
        return right - left;
    }
};