牛客第四次多校Maximum Mode

链接：https://www.nowcoder.com/acm/contest/142/G
来源：牛客网

题目描述

The mode of an integer sequence is the value that appears most often. Chiaki has n integers a ₁,a ₂,...,a _n. She woud like to delete exactly m of them such that: the rest integers have only one mode and the mode is maximum.

输入描述:

There are multiple test cases. The first line of input contains an integer T, indicating the number of test cases. For each test case:
The first line contains two integers n and m (1 ≤ n ≤ 10^5, 0 ≤ m < n) -- the length of the sequence and the number of integers to delete.

The second line contains n integers a1,a2, ..., an(1 ≤ ai ≤ 10^9)denoting the sequence.It is guaranteed that the sum of all n does not exceed 10^6

输出描述:

For each test case, output an integer denoting the only maximum mode, or -1 if Chiaki cannot achieve it.

示例1

输入

5
5 0
2 2 3 3 4
5 1
2 2 3 3 4
5 2
2 2 3 3 4
5 3
2 2 3 3 4
5 4
2 2 3 3 4

输出

-1
3
3
3
4

 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 const int MAXN=1e5+10;
 4 int a[MAXN];
 5 map<int, int>ma;
 6 map<int ,int>mb;
 7 int sum[MAXN],cnt[MAXN];
 8 int main()
 9 {
10     int _;
11     scanf("%d",&_);
12     while(_--)
13     {
14         ma.clear();
15         int n,m;
16         scanf("%d%d",&n,&m);
17         for(int i=1;i<=n;i++)
18         {
19             scanf("%d",&a[i]);
20             ma[a[i]]++;
21             sum[i]=0;
22             cnt[i]=0;
23         }
24         for(auto &i:ma) cnt[i.second]++;
25         for (int i = n-1; i ; i--) {   //求出后缀和
26             cnt[i]+=cnt[i+1];
27             sum[i]=sum[i+1]+cnt[i];//从后向前进行，如果一个数出现n次，在向前加的过程中每次都会加n次。保证后缀和正确
28         }
29         int MAX=-1;
30         for(auto &i:ma){
31             if(sum[i.second]-1<=m) MAX=max(MAX,i.first);//枚举答案，-1是因为只要保证当前这个众数比其他的多一即可
32         }
33         printf("%d\n",MAX);
34     }
35     return 0;
36 }

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