最大独立集模板

#include<iostream>
#include<cstdio>
#include<cstring>
 
using namespace std;
 
const int maxn=55;
 
int n;
bool g[maxn][maxn];
bool found;
int len[maxn],list[maxn][maxn],ans,mc[maxn];
 
void dfs(int size)
{
    if(len[size]==0){
        if(size>ans){
            ans=size;
            found=true;
        }
    }
    for(int k=0;k<len[size]&&!found;k++){
        if(size+len[size]-k<=ans){
            break;
        }
        int i=list[size][k];
        if(size+mc[i]<=ans){
            break;
        }
        len[size+1]=0;
        for(int j=k+1;j<len[size];j++){
            if(g[i][list[size][j]]){
                list[size+1][len[size+1]++]=list[size][j];
            }
        }
        dfs(size+1);
    }
}
 
void max_cluster()
{
    mc[n]=ans=1;
    for(int i=n-1;i;i--){
        found=false;
        len[1]=0;
        for(int j=i+1;j<=n;j++){
            if(g[i][j]){
                list[1][len[1]++]=j;
            }
        }
        dfs(1);
        mc[i]=ans;
    }
}
 
int main()
{
    while(scanf("%d",&n)!=EOF&&n){
        for(int i=1;i<=n;i++){
            for(int j=1;j<=n;j++){
                scanf("%d",&g[i][j]);
            }
        }
        max_cluster();
        printf("%d\n",ans);
    }
    return 0;
}