UVALive 6322 最大匹配

思路：枚举每个位置的最小字符，用最大匹配判断是否可行

#include<iostream>
#include<algorithm>
#include<cstring>
#include<cstdio>
#include<cmath>
#define Maxn 1010
using namespace std;
int match[Maxn],vi[Maxn],num[Maxn],g[Maxn][Maxn],f[Maxn],ch[Maxn],n,le;
void init()
{
    memset(match,-1,sizeof(match));
    memset(vi,0,sizeof(vi));
    memset(num,0,sizeof(num));
    memset(g,0,sizeof(g));
    memset(f,0,sizeof(f));
    memset(ch,0,sizeof(ch));
}
int dfs(int u)
{
    int i;
    for(i=1;i<=n;i++) if(!f[i]&&!vi[i]&&g[u][i]){
        vi[i]=1;
        if(match[i]==-1||dfs(match[i])){
            match[i]=u;
            return 1;
        }
    }
    return 0;
}
int OK()
{
    int i,ans=0;
    memset(match,-1,sizeof(match));
    for(i=1;i<=n;i++){
        if(ch[i]) continue;
        memset(vi,0,sizeof(vi));
        if(dfs(i))
            ans++;
    }
    return ans==le;
}
int main()
{
    int i,j,t,l,k;
    char str[Maxn],s[Maxn];
    scanf("%d",&t);
    while(t--){
        init();
        scanf("%s",str+1);
        n=strlen(str+1);
        sort(str+1,str+1+n);
        for(i=1;i<=n;i++){
            scanf("%s",s);
            l=strlen(s);
            for(j=1;j<=n;j++){
                for(k=0;k<l;k++){
                    if(str[j]==s[k]){
                        g[i][j]=1;
                        //cout<<i<<" "<<j<<endl;
                    }
                }
            }
        }
        int ans=0;
        for(i=1;i<=n;i++){
            memset(vi,0,sizeof(vi));
            if(dfs(i))
                ans++;
        }
        if(ans<n){
            printf("NO SOLUTION\n");
            continue;
        }
        memset(match,-1,sizeof(match));
        le=n;
        for(i=1;i<=n;i++){
            for(j=1;j<=n;j++)if(!f[j]&&g[i][j]){
                ch[i]=j;
                f[j]=1;
                le--;
                if(OK())
                    break;
                le++;
                f[j]=0;
            }
        }
        for(i=1;i<=n;i++)
            printf("%c",str[ch[i]]);
        puts("");
    }
    return 0;
}