牛客网-剑指office-数字在排序数组中出现的次数

题目:统计一个数字在排序数组中出现的次数。
解法一:
思路:暴力解法。遍历一遍数组,统计该数字出现的次数。

class Solution {
public:
    int GetNumberOfK(vector<int> data ,int k) {
        int count = 0;
        for (int i= 0;i<data.size();++i)
        {
            if(data[i]==k)
                count++;
        }
        return count;
    }
};

解法二:
思路:两次二分法,分别确定数字出现的首尾。作差即为答案。

class Solution {
public:
	int GetNumberOfK(vector<int> data, int k) {
		int l = 0;
		int r = data.size();
		while (l < r)
		{
			int mid = (l + r) / 2;
			if (data[mid] < k) l = mid + 1;
			else
				r = mid;
		}
		int left = l;
		l = 0;
		r = data.size();
		while (l < r)
		{
			int mid = (l + r) / 2;
			if (data[mid] > k) r=mid;
			else
				l = mid+1;
		}
		return r-left;
	}
};

python的解法:
暴力法:

# -*- coding:utf-8 -*-
class Solution:
    def GetNumberOfK(self, data, k):
        # write code here
        count = 0
        for num in data:
            if num == k:
                count += 1
        return count

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转载自blog.csdn.net/qq_43387999/article/details/91126657
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