题解 | 数字在升序数组中出现的次数

class Solution {
public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param nums int整型vector 
     * @param k int整型 
     * @return int整型
     */
    int GetNumberOfK(vector<int>& nums, int k) {
        int left = 0;
        int right = nums.size()-1;
        int Index = 0;
        bool flag = false;
        while(left <= right){
            int mid = left + (right - left) / 2;
            if(nums[mid] > k){
                right = mid -1;
            }
            else if(nums[mid] < k){
                left = mid + 1;
            }
            else{
                Index = mid;
                flag = true;
                break;
            }
        }
        if(!flag) return 0;
        int res = 0;
        for( int i = Index; i >= 0; i --){
            if(nums[i] == k) res ++;
            else break;
        }
        for( int i = Index; i < nums.size(); i ++){
            if( nums[i] == k) res ++;
            else break;
        }
        return res - 1;
    }
};