剑指 Offer 53

题目描述

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

来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/zai-pai-xu-shu-zu-zhong-cha-zhao-shu-zi-lcof

代码实现

class Solution {
public:
    int search(vector<int>& nums, int target) {
        int i, j, m;
        int left, right;
        // Search the left boundary
        i = 0; j = nums.size() - 1;
        while(i <= j) {
            m = (i + j) / 2;
            if(nums[m] < target)
                i = m + 1;
            else
                j = m - 1;
        }
        left = j;
        // Search the right boundary
        i = 0; j = nums.size() - 1;
        while(i <= j) {
            m = (i + j) / 2;
            if(nums[m] > target)
                j = m - 1;
            else
                i = m + 1;
        }
        right = i;
        return right - left - 1;
    }
};