Codeforces Round #671 (Div. 2) C. Killjoy

outputstandard output
A new agent called Killjoy invented a virus COVID-2069 that infects accounts on Codeforces. Each account has a rating, described by an integer (it can possibly be negative or very large).

Killjoy’s account is already infected and has a rating equal to x. Its rating is constant. There are n accounts except hers, numbered from 1 to n. The i-th account’s initial rating is ai. Any infected account (initially the only infected account is Killjoy’s) instantly infects any uninfected account if their ratings are equal. This can happen at the beginning (before any rating changes) and after each contest. If an account is infected, it can not be healed.

Contests are regularly held on Codeforces. In each contest, any of these n accounts (including infected ones) can participate. Killjoy can’t participate. After each contest ratings are changed this way: each participant’s rating is changed by an integer, but the sum of all changes must be equal to zero. New ratings can be any integer.

Find out the minimal number of contests needed to infect all accounts. You can choose which accounts will participate in each contest and how the ratings will change.

It can be proven that all accounts can be infected in some finite number of contests.

Input
The first line contains a single integer t (1≤t≤100) — the number of test cases. The next 2t lines contain the descriptions of all test cases.

The first line of each test case contains two integers n and x (2≤n≤103, −4000≤x≤4000) — the number of accounts on Codeforces and the rating of Killjoy’s account.

The second line of each test case contains n integers a1,a2,…,an (−4000≤ai≤4000) — the ratings of other accounts.

Output
For each test case output the minimal number of contests needed to infect all accounts.

Example
inputCopy
3
2 69
68 70
6 4
4 4 4 4 4 4
9 38
-21 83 50 -59 -77 15 -71 -78 20
outputCopy
1
0
2
Note
In the first test case it’s possible to make all ratings equal to 69. First account’s rating will increase by 1, and second account’s rating will decrease by 1, so the sum of all changes will be equal to zero.

In the second test case all accounts will be instantly infected, because all ratings (including Killjoy’s account’s rating) are equal to 4.

这题主要是题意有些许难懂 （可能对我来说）
如果全部相同 那当然不需要次数 0 即可
否则 则计算每个值ai 和 期望x 的差距总值 如果值为0 只需要次数1

如果值不为0 则将n - 1个数都换成 x ，再更新剩下的换成x 需要两步
特别的 如果其中有个剩下的 等于x 则不需要再更新了 只需要一步即可

#include <bits/stdc++.h>

using namespace std;

#define LL long long

int main(){
    int t;

    cin >> t;

    while(t --){
        int n , x;
        cin >> n >> x;
        
        vector <int> a(n);

        for(int i = 0;i < n;i ++){
            cin >> a[i];
        }

        LL sum = 0;
        bool flag = 0,is_in = 0;

        for(int i = 0;i < n;i ++){
            sum += a[i] - x;
            if(a[i] == x){
                is_in = 1;
            }
            if(a[i] != x){
                flag = 1;
            }
        }

        int res = 0;
        if(!flag){
            res = 0;
        }else if(sum == 0 || is_in){
            res = 1;
        }else{
            res = 2;
        }

        cout << res << '\n';
    }
    return 0;
}

标签：rating,account,Codeforces,accounts,each,infected,Div,Killjoy
来源： https://blog.csdn.net/weixin_44144278/article/details/110150698