poj-1459 Power Network

版权声明：最后一年，加油~ https://blog.csdn.net/zzti_xiaowei/article/details/81088294

[题目链接]

思路：最大流模板题，但是还是手残，敲的磕磕绊绊，思路就不说啦~~

代码：

#include<iostream>
#include<cstdio>
#include<cstring>
#include<vector>
#include<queue>
#include<vector>
using namespace std;
typedef long long ll;
const int inf=0x3f3f3f3f;
const int Max_n=1e4+10;

int n,np,nc,m;
struct edge{
    int to,cap,rev;
    edge(int t,int c,int r):to(t),cap(c),rev(r){}
};
vector<edge>G[Max_n];
int level[Max_n];
int iter[Max_n];

void add_edge(int from,int to,int cap){
    G[from].push_back(edge(to,cap,G[to].size()));
    G[to].push_back(edge(from,0,G[from].size()-1));
}

int bfs(int s){
    memset(level,-1,sizeof(level));
    level[s]=0;
    queue<int>que;
    que.push(s);
    while(!que.empty()){
        int v=que.front();que.pop();
        for(int i=0;i<G[v].size();i++){
            edge &e=G[v][i];
            if(e.cap>0&level[e.to]<0){
                level[e.to]=level[v]+1;
                que.push(e.to);
            }
        }
    }
}

int dfs(int v,int t,int f){
    if(v==t)return f;
    for(int &i=iter[v];i<G[v].size();i++){
        edge &e=G[v][i];
        if(e.cap>0&&level[v]<level[e.to]){
            int d=dfs(e.to,t,min(e.cap,f));
            if(d>0){
                e.cap-=d;
                G[e.to][e.rev].cap+=d;
                return d;
            }
        }
    }
    return -1;
}

int max_flow(int s,int t){
    int flow=0;
    while(true){
        bfs(s);
        if(level[t]<0)return flow;
        memset(iter,0,sizeof(iter));
        int f;
        while((f=dfs(s,t,inf))>0){
            flow+=f;
        }
    }
}

int main()
{
    while(~scanf("%d%d%d%d",&n,&np,&nc,&m)){
        for(int i=0;i<=Max_n;i++)G[i].clear();
        int a,b,c;
        for(int i=0;i<m;i++){
            scanf(" (%d,%d)%d",&a,&b,&c);
            add_edge(a,b,c);
        }
        int s=110,t=120;
        for(int i=0;i<np;i++){
            scanf(" (%d)%d",&a,&b);
            add_edge(s,a,b);
        }
        for(int i=0;i<nc;i++){
            scanf(" (%d)%d",&a,&b);
            add_edge(a,t,b);
        }
        printf("%d\n",max_flow(s,t));
    }
    return 0;
}