题解 | #数字在升序数组中出现的次数#

主要思路二分查找到K的位置 ， 然后再计算有几个K

注意边界情况处理 ， 以及是小于还是小于等于

 public int GetNumberOfK(int [] array , int k) {
        int len = array.length;
        if (len == 0|| array == null){
            return 0;
        }
        int left = 0;
        int right = len -1;
        int kTh = 0;
        while (left<=right){
            int mid = left + (right -left)/2;
            int num = array[mid];
            if (num == k){
                if(mid == 0){
                    kTh = mid;
                    break;
                }
                while (left>=0&&(mid>=0)&&(mid-1>=0)&&array[mid] == array[--mid]);

                kTh = mid>0?mid+1:mid;
                break;
            }else  if (k<num){
                right =mid-1;
            }else  if (k>num){
                left = mid+1;
            }
        }
        int count = 0 ;
        int i = kTh;
            while (i<=len-1&&array[i] == k){
                count++;
                i++;
            }

        return  count;
    }
}