hdu5305 Friends
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Problem Description
There are n people and m pairs of friends. For every pair of friends, they can choose to become online friends (communicating using online applications) or offline friends (mostly using face-to-face communication). However, everyone in these n people wants to have the same number of online and offline friends (i.e. If one person has x onine friends, he or she must have x offline friends too, but different people can have different number of online or offline friends). Please determine how many ways there are to satisfy their requirements.
Input
The first line of the input is a single integer T (T=100) , indicating the number of testcases.
For each testcase, the first line contains two integersn (1≤n≤8) and m (0≤m≤n(n−1)2) , indicating the number of people and the number of pairs of friends, respectively. Each of the next m lines contains two numbers x and y , which mean x and y are friends. It is guaranteed that x≠y and every friend relationship will appear at most once.
For each testcase, the first line contains two integers
Output
For each testcase, print one number indicating the answer.
Sample Input
23 31 22 33 14 41 22 33 44 1
Sample Output
02
这题是一道简单搜索题,我用dfs(idx,num1,num2)表示当前搜索的是idx的关系,num1表示虚拟关系的个数,num2表示现实关系的个数。
#include<iostream>#include<stdio.h>#include<stdlib.h>#include<string.h>#include<math.h>#include<vector>#include<map>#include<set>#include<queue>#include<stack>#include<string>#include<algorithm>using namespace std;#define maxn 100060#define ll long longint num[10],gra[10][10],n,m,sum,guanxi[10][10],vis1[10],vis2[10];void dfs(int idx,int num1,int num2,int pos,int from){ int i,j; if(num1==num2 && num1+num2==num[idx]){ if(idx==n){ sum++;return; } else{ idx++;num1=num2=0; for(i=1;i<=n;i++){ if(guanxi[idx][i]==1){ num2++; } else if(guanxi[idx][i]==0){ num1++; } } dfs(idx,num1,num2,idx+1,0); } return ; } if(num1>num[idx]/2 || num2>num[idx]/2)return; for(i=pos;i<=n;i++){ if(gra[i][idx] && guanxi[i][idx]==-1){ guanxi[i][idx]=guanxi[idx][i]=0; dfs(idx,num1+1,num2,i+1,1); guanxi[i][idx]=guanxi[idx][i]=1; dfs(idx,num1,num2+1,i+1,2); guanxi[i][idx]=guanxi[idx][i]=-1;break; } } return;}int main(){ int i,j,T,c,d,flag; scanf("%d",&T); while(T--) { scanf("%d%d",&n,&m); if(n==1){ printf("1\n");continue; } memset(num,0,sizeof(num)); memset(gra,0,sizeof(gra)); for(i=1;i<=m;i++){ scanf("%d%d",&c,&d); gra[c][d]=gra[d][c]=1;num[c]++;num[d]++; } flag=1; for(i=1;i<=n;i++){ if(num[i]&1){ flag=0;break; } } if(!flag){ printf("0\n");continue; } sum=0; memset(guanxi,-1,sizeof(guanxi)); dfs(1,0,0,2,0); printf("%d\n",sum); } return 0;}
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