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

 

class Solution {
    public int search(int[] nums, int target) {
        int left = left(nums, target);
        int right = right(nums, target);
        
        int count = right - left - 1;
            
        return  count;
    }
    
    private int left(int[] nums, int target) {
        int left = 0, right = nums.length - 1;
        while(left <= right) {
            int mid = (left + ((right - left) >> 1));
            if(nums[mid] >= target) {
                right = mid - 1;
            } else {
                left = mid + 1;
            }
        }
        
        return right;
    }
    
    private int right(int[] nums, int target) {
        int left = 0, right = nums.length - 1;
        while(left <= right) {
            int mid = (left + ((right - left) >> 1));
            if(nums[mid] <= target) {
                left = mid + 1;
            } else {
                right= mid - 1;
            }
        }
        
        return left;
    }    
}


O(n)
class Solution {
    public int search(int[] nums, int target) {
        int count = 0;
        for(int i = 0; i < nums.length; i++) {
            if(nums[i] == target) {
                count++;
            }
        }
        return count;
    }
}

　　

 

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
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