【二分图】专题

refer：http://blog.youkuaiyun.com/hackbuteer1/article/details/7398008

http://poj.org/problem?id=1469

#include <iostream>
#include <math.h>
#include <algorithm>
#include <string.h>
#include <stdio.h>
using namespace std;

bool g[110][310];
bool visit[310];
int match[310];
int p, n;

bool dfs(int u)
{
    for(int i = 1; i <= n; i++){
        if(g[u][i] && !visit[i]){
            visit[i] = true;
            if(match[i] == -1 || dfs(match[i])){
                match[i] = u;
                return true;
            }
        }
    }
    return false;
}


int main()
{
    int t;
    scanf("%d", &t);
    while(t--)
    {
        scanf("%d%d", &p, &n);
        for(int i = 1; i <= p; i++){
            for(int j = 1; j <= n; j++){
                g[i][j] = false;
            }
        }
        for(int i = 1; i <= n; i++)
            match[i] = -1;
        bool flag = false;
        for(int i = 1; i <= p; i++) //input
        {
            int times;
            scanf("%d", ×);
            if(times == 0) flag = true;
            while(times--){
                int a;
                scanf("%d", &a);
                g[i][a] = true;
            }
        }

        if(!flag){
            int ans = 0;
            for(int i = 1; i <= p; i++){
                memset(visit, false, sizeof(visit));
                if(dfs(i)) ans++;
            }
            if(ans == p) puts("YES");
            else puts("NO");
        }
        else
            puts("NO");
    }
    return 0;
}

http://acm.hdu.edu.cn/showproblem.php?pid=2444

#include <iostream>
#include <math.h>
#include <algorithm>
#include <string.h>
#include <stdio.h>
using namespace std;
#define white 1
#define black 0
#define none -1

int n;
bool g[220][220];
int color[220];
bool visite[220];

bool DFS(int u)
{
    for(int i = 0; i <= n; i++)
    {
        if(g[u][i])
        {
            if(color[i] == none)
            {
                color[i] = 1 - color[u];
                if(DFS(i) == true) return true;
            }
            else if(color[u] == color[i]) return true;
        }
    }
    return false;
}

bool isbigr()
{
    memset(color, -1, sizeof(color));
    color[1] = white;
    //printf("%d %d", color[1], color[3]);
    if(DFS(1)) return true;
    return false;
}

bool match(int u)
{
    for(int i = 1; i <= n; i++)
    {
        if(g[u][i] && !visite[i])
        {
            visite[i] = true;
            if(color[i] == -1 || match(color[i]))
            {
                color[i] = u;
                return true;
            }
        }
    }
    return false;
}
int main()
{
    int m;
    while(scanf("%d %d", &n, &m) != -1)
    {
        for(int i = 0; i <= n; i++)
            for(int j = 0; j <= n; j++)
                g[i][j] = false;

        while(m--)
        {
            int a, b;
            scanf("%d %d", &a, &b);
            g[a][b] = true;
        }

        if(isbigr()) puts("No");
        else
        {
            for(int i = 0; i <= n; i++)
                color[i] = -1;
            int ans = 0;

            for(int i = 1; i<= n; i++)
            {
                memset(visite, false, sizeof(visite));
                if(match(i)) ans++;
            }
            printf("%d\n", ans);
        }
    }

}