剑指 Offer 53 - I. 在排序数组中查找数字 I(二分查找)

剑指 Offer 53 - I. 在排序数组中查找数字 I

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

 

提示：

• 0 <= nums.length <= 105
• -109 <= nums[i] <= 109
• nums 是一个非递减数组
• -109 <= target <= 109

 

注意：本题与主站 34 题相同（仅返回值不同）：https://leetcode-cn.com/problems/find-first-and-last-position-of-element-in-sorted-array/

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