poj 1459 Power Network(最大流)

http://poj.org/problem?id=1459

题意略去，没什么坑。只是多源多汇，加上超级源点和汇点建图就行。

Dinic 235ms

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

const int INF = 0x3f3f3f3f;

int n,m,np,nc;
int map[110][110];
char str[20];
int s,t;
int dis[210];

bool bfs()      //建立层次图
{
    memset(dis,-1,sizeof(dis));
    dis[s] = 0;
    queue <int> que;
    while(!que.empty()) que.pop();
    que.push(s);

    while(!que.empty())
    {
        int u = que.front();
        que.pop();
        for(int i = 0; i <= n+1; i++)
        {
            if(dis[i] == -1 && map[u][i])
            {
                dis[i] = dis[u]+1;
                que.push(i);
            }
        }
    }
    if(dis[t] > 0) return true;
    return false;
}

int dfs(int s, int delta = INF) //寻找最小残量
{
    if(s == t || delta == 0)
        return delta;
    int ans;
    int ret = 0;
    for(int i = 0; i <= n+1; i++)
    {
        if(map[s][i] && dis[i] == dis[s]+1 && (ans = dfs(i,min(delta,map[s][i])) ) )
        {
            map[s][i] -= ans;
            map[i][s] += ans;
            ret += ans;
            delta -= ans;
        }
    }
    return ret;
}

int main()
{
    while(~scanf("%d %d %d %d",&n,&np,&nc,&m))
    {
        memset(map,0,sizeof(map));
        int u,v,w;
        s = n;
        t = n+1;
        while(m--)
        {
            scanf("%s",str);
            sscanf(str,"(%d,%d)%d",&u,&v,&w);
            map[u][v] = w;
        }
        while(np--)
        {
            scanf("%s",str);
            sscanf(str,"(%d)%d",&v,&w);
            map[n][v] = w;
        }
        while(nc--)
        {
            scanf("%s",str);
            sscanf(str,"(%d)%d",&u,&w);
            map[u][n+1] = w;
        }

        int ans = 0;

        while(bfs())
        {
            ans += dfs(s);
        }
        printf("%d\n",ans);

    }
    return 0;

}

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

const int INF = 0x3f3f3f3f;

int n,np,nc,m,s,t;
int map[110][110];
char str[20];
int a[110],pre[110],flow[110][110],mf;
queue <int>que;

void maxflow()
{
    memset(flow,0,sizeof(flow));
    mf = 0;
    while(1)
    {
        memset(a,0,sizeof(a));
        while(!que.empty()) que.pop();
		a[s] = INF;
        que.push(s);

        while(!que.empty())
        {
            int u = que.front();
            que.pop();
            for(int v = 0; v <= n+1; v++)
            {
                if(!a[v] && map[u][v] > flow[u][v])
                {
                    pre[v] = u;
                    que.push(v);
                    if(a[u] < map[u][v]-flow[u][v])
                        a[v] = a[u];
                    else a[v] = map[u][v]-flow[u][v];
                }
            }
        }
        if(a[t] == 0) break;
        for(int u = t; u != s; u = pre[u])
        {
        	flow[ pre[u] ][u] += a[t];
        	flow[u][ pre[u] ] -= a[t];
        }
        mf += a[t];
    }
}

int main()
{
    while(~scanf("%d %d %d %d",&n,&np,&nc,&m))
    {
        memset(map,0,sizeof(map));
        int u,v,w;
        s = n;
        t = n+1;

        while(m--)
        {
            scanf("%s",str);
            sscanf(str,"(%d,%d)%d",&u,&v,&w);
            map[u][v] = w;
        }
        while(np--)
        {
            scanf("%s",str);
            sscanf(str,"(%d)%d",&v,&w);
            map[n][v] = w;
        }
        while(nc--)
        {
            scanf("%s",str);
            sscanf(str,"(%d)%d",&u,&w);
            map[u][n+1] = w;
        }
		maxflow();
		printf("%d\n",mf);

    }
    return 0;

}

poj 1459 Power Network(最大流),古老的榕树,5-wow.com