解题思路：二分查找

题解一

class Solution {public int countTarget(int[] scores, int target) {// 搜索右边界 rightint i = 0, j = scores.length - 1;while(i <= j) {int m = (i + j) / 2;if(scores[m] <= target) i = m + 1;else j = m - 1;}int right = i;// 若数组中无 target ，则提前返回if(j >= 0 && scores[j] != target) return 0;// 搜索左边界 righti = 0; j = scores.length - 1;while(i <= j) {int m = (i + j) / 2;if(scores[m] < target) i = m + 1;else j = m - 1;}int left = j;return right - left - 1;}
}

题解二（优化版）

class Solution {public int countTarget(int[] scores, int target) {return helper(scores, target) - helper(scores, target - 1);}int helper(int[] scores, int tar) {int i = 0, j = scores.length - 1;while(i <= j) {int m = (i + j) / 2;if(scores[m] <= tar) i = m + 1;else j = m - 1;}return i;}
}