HDU 3829 Cat VS Dog(二分图最大独立集)

#include <bits/stdc++.h>
#define maxn 505 * 505
using namespace std;
struct Node{
    int to,next;
}Edge[maxn];
struct node{
    string str_l, str_d;
}edge[maxn];
int head[maxn],num;
int pre[maxn];
bool vis[maxn];
int n,m,p,cnt;

void init(){
    memset(head,-1,sizeof(head));
    num = 0;
}

void add(int u, int v){
    Edge[num].to = v;
    Edge[num].next = head[u];
    head[u] = num ++;
}

bool dfs(int u){
    for(int i=head[u];i!=-1;i=Edge[i].next){
        int v = Edge[i].to;
        if(!vis[v]){
            vis[v] = true;
            if(pre[v] == -1 || dfs(pre[v])){
                pre[v] = u;
                return true;
            }
        }
    }
    return false;
}

int solve(){
    int sum = 0;
    memset(pre,-1,sizeof(pre));
    for(int i=1;i<=p;i++){
        memset(vis,false,sizeof(vis));
        if(dfs(i)) sum ++;
    }
    return sum;
}

int main()
{
    while(~scanf("%d%d%d",&n,&m,&p)){
        init();
        for(int i=1;i<=p;i++){
            cin>>edge[i].str_l>>edge[i].str_d;
        }
        for(int i=1;i<=p;i++){
            for(int j=1;j<=p;j++){
                if(edge[i].str_l == edge[j].str_d || edge[i].str_d == edge[j].str_l){
                    add(i, j);
                }
            }
        }
        int ans = solve();
        printf("%d\n",p - ans / 2);
    }
    return 0;
}