Codeforces Round #338 (Div. 2) A. Bulbs （python and c++）

本文链接：https://blog.youkuaiyun.com/just_for_your_smile/article/details/50775045

本文探讨了如何通过按钮操作来点亮所有圣诞灯泡的问题，包括输入数据解析、逻辑判断和输出结果展示。

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Vasya wants to turn on Christmas lights consisting of m bulbs. Initially, all bulbs are turned off. There aren buttons, each of them is connected to some set of bulbs. Vasya can press any of these buttons. When the button is pressed, it turns on all the bulbs it's connected to. Can Vasya light up all the bulbs?

If Vasya presses the button such that some bulbs connected to it are already turned on, they do not change their state, i.e. remain turned on.

Input

The first line of the input contains integers n andm (1 ≤ n, m ≤ 100) — the number of buttons and the number of bulbs respectively.

Each of the next n lines contains x_i (0 ≤ x_i ≤ m) — the number of bulbs that are turned on by thei-th button, and then x_i numbers y_ij (1 ≤ y_ij ≤ m) — the numbers of these bulbs.

Output

If it's possible to turn on all m bulbs print "YES", otherwise print "NO".

Examples

Input

Output

YES


       
       
        
        
         
         Input
        
        
        
        3 3
1 1
1 2
1 1

       
       
       
       
        
        
         
         Output
        
        
        
        NO

       
       
       
       
        
        Note
       
       
In the first sample you can press each button once and turn on all the bulbs. In the 2 sample it is impossible to turn on the 3-rd lamp.

#include<bits/stdc++.h>
using namespace std;

const int maxn = 200;
int a[maxn];

int main() {

    int n,m;
    cin>>n>>m;
    int num;
    while(n--) {
        cin>>num;
        while(num--) {
            int i;
            cin>>i;
            a[i] = 1;
        }
    }
    int ans= 0;
    for(int i = 1; i <= m; i++) {
        ans += a[i];
    }
    if(ans == m)
        cout<<"YES"<<endl;
    else
        cout<<"NO"<<endl;

}

直接打表就可以了

python代码；

# _*_ coding:utf-8 _*_
import sys
a = [0 for i in range(200)]
b = []
n,m = map(int, sys.stdin.readline().split())
while n >=1 :
    b = map(int, sys.stdin.readline().split())
    for i in range(b[0]) :
        a[b[i+1]] = 1;
    n -= 1
ans = 0
for i in range(1, m+1):
    ans += a[i] 
print 'YES' if ans == m  else 'NO'

c++ 代码