CodeForces

http://codeforces.com/contest/868/problem/C

题意：有n道题目，k支队伍，现在要从n道题中取x道题(x>0)作为比赛题。要求这x道题中，每支队伍所知的题目不超过x/2。求是否存在这样的x。

题解：官方的tag给出的是dp。当时我做的时候看到k最大就是4，干脆就暴力了。中间bool没有初始化，wa一发。代码打得好长，ide中间还崩溃了又得重新打。看来得养成ctrl+s的好习惯。大致思路就是如果存在都是0的情况，则一定存在这样的x(一共取2题，取该题以及任何其他一题即可)。又例如k=2的情况，如果有一题是0 1，另一题是1 0，也是可以的。依次类推，具体看代码。(dp代码待补)

代码：

#include<bits/stdc++.h>#define debug cout<<"aaa"<<endl#define d(a) cout<<a<<endl#define pb push_back#define mem(a,b) memset(a,b,sizeof(a))#define LL long long#define lson l,mid,root<<1#define rson mid+1,r,root<<1|1#define MIN_INT (-2147483647-1)#define MAX_INT 2147483647#define MAX_LL 9223372036854775807i64#define MIN_LL (-9223372036854775807i64-1)using namespace std;const int N = 100000 + 5;const int mod = 1000000000 + 7;const double eps = 1e-8;int a[N][10];int main(){int n,k,cnt;cin>>n>>k;for(int i=1;i<=n;i++){for(int j=1;j<=k;j++){cin>>a[i][j];}}if(k==1){for(int i=1;i<=n;i++){if(a[i][1]==0){puts("YES");return 0;}}puts("NO");}else if(k==2){bool f01=0,f10=0;for(int i=1;i<=n;i++){if(a[i][1]==0&&a[i][2]==0){puts("YES");return 0;}else if(a[i][1]==0&&a[i][2]==1){f01=1;}else if(a[i][1]==1&&a[i][2]==0){f10=1;}}if(f01&&f10){puts("YES");}else{puts("NO");}}else if(k==3){bool f001=0,f010=0,f100=0,f110=0,f101=0,f011=0;for(int i=1;i<=n;i++){if(a[i][1]==0&&a[i][2]==0&&a[i][3]==0){puts("YES");return 0;}else if(a[i][1]==0&&a[i][2]==0&&a[i][3]==1){f001=1;}else if(a[i][1]==0&&a[i][2]==1&&a[i][3]==0){f010=1;}else if(a[i][1]==1&&a[i][2]==0&&a[i][3]==0){f100=1;}else if(a[i][1]==1&&a[i][2]==1&&a[i][3]==0){f110=1;}else if(a[i][1]==1&&a[i][2]==0&&a[i][3]==1){f101=1;}else if(a[i][1]==0&&a[i][2]==1&&a[i][3]==1){f011=1;}}if((f001&&f010)||(f001&&f100)||(f001&&f110)){puts("YES");}else if((f010&&f100)||(f010&&f001)||(f010&&f101)){puts("YES");}else if((f100&&f001)||(f100&&f010)||(f100&&f011)){puts("YES");}else{puts("NO");}}else if(k==4){bool f0001=0,f0010=0,f0100=0,f1000=0,f1100=0,f1010=0,f0110=0,f0011=0,f0101=0,f1001=0,f1110=0,f1101=0,f1011=0,f0111=0;for(int i=1;i<=n;i++){if(a[i][1]==0&&a[i][2]==0&&a[i][3]==0&&a[i][4]==0){puts("YES");return 0;}else if(a[i][1]==0&&a[i][2]==0&&a[i][3]==0&&a[i][4]==1){f0001=1;}else if(a[i][1]==0&&a[i][2]==0&&a[i][3]==1&&a[i][4]==0){f0010=1;}else if(a[i][1]==0&&a[i][2]==1&&a[i][3]==0&&a[i][4]==0){f0100=1;}else if(a[i][1]==1&&a[i][2]==0&&a[i][3]==0&&a[i][4]==0){f1000=1;}else if(a[i][1]==1&&a[i][2]==1&&a[i][3]==0&&a[i][4]==0){f1100=1;}else if(a[i][1]==1&&a[i][2]==0&&a[i][3]==1&&a[i][4]==0){f1010=1;}else if(a[i][1]==1&&a[i][2]==0&&a[i][3]==0&&a[i][4]==1){f1001=1;}else if(a[i][1]==0&&a[i][2]==1&&a[i][3]==0&&a[i][4]==1){f0101=1;}else if(a[i][1]==0&&a[i][2]==1&&a[i][3]==1&&a[i][4]==0){f0110=1;}else if(a[i][1]==0&&a[i][2]==0&&a[i][3]==1&&a[i][4]==1){f0011=1;}else if(a[i][1]==1&&a[i][2]==1&&a[i][3]==1&&a[i][4]==0){f1110=1;}else if(a[i][1]==1&&a[i][2]==1&&a[i][3]==0&&a[i][4]==1){f1101=1;}else if(a[i][1]==1&&a[i][2]==0&&a[i][3]==1&&a[i][4]==1){f1011=1;}else if(a[i][1]==0&&a[i][2]==1&&a[i][3]==1&&a[i][4]==1){f0111=1;}}if((f0001&&f0010)||(f0001&&f0100)||(f0001&&f1000)||(f0001&&f0110)||(f0001&&f1010)||(f0001&&f1100)||(f0001&&f1110)){puts("YES");}else if((f0010&&f0001)||(f0010&&f0100)||(f0010&&f1000)||(f0010&&f0101)||(f0010&&f1100)||(f0010&&f1001)||(f0010&&f1101)){puts("YES");}else if((f0100&&f0001)||(f0100&&f0010)||(f0100&&f1000)||(f0100&&f1010)||(f0100&&f1001)||(f0100&&f0011)||(f0100&&f1011)){puts("YES");}else if((f1000&&f0001)||(f1000&&f0010)||(f1000&&f0100)||(f1000&&f0110)||(f1000&&f0011)||(f1000&&f0101)||(f1000&&f0111)){puts("YES");}else if((f0011&&f1100)||(f0101&&f1010)||(f1001&&f0110)){puts("YES");}else{puts("NO");}}return 0;}