zoj 2314 Reactor Cooling 无源汇网络流

终于知道什么是无源汇网络流的题了。。。

#include<iostream>
#include<algorithm>
#include<iostream>
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<vector>
#include<queue>
#include<cmath>
using namespace std;
#define ll long long
#define inf 0x3f3f3f3f
int dir[4][2]={0,1,0,-1,1,0,-1,0};


int n,m;
int c[305];
int lo[50000];


const int maxnode = 300 + 5;
const int maxedge = 2*50000 + 5;
const int oo = 1000000000;
int node, src, dest, nedge;
int head[maxnode], point[maxedge], next1[maxedge], flow[maxedge], capa[maxedge];//point[x]==y表示第x条边连接y，head，next为邻接表，flow[x]表示x边的动态值，capa[x]表示x边的初始值
int dist[maxnode], Q[maxnode], work[maxnode];//dist[i]表示i点的等级
void init(int _node, int _src, int _dest){//初始化，node表示点的个数，src表示起点，dest表示终点
    node = _node;
    src = _src;
    dest = _dest;
    for (int i = 0; i < node; i++) head[i] = -1;
    nedge = 0;
}
void addedge(int u, int v, int c1, int c2){//增加一条u到v流量为c1，v到u流量为c2的两条边
    point[nedge] = v, capa[nedge] = c1, flow[nedge] = 0, next1[nedge] = head[u], head[u] = (nedge++);
    point[nedge] = u, capa[nedge] = c2, flow[nedge] = 0, next1[nedge] = head[v], head[v] = (nedge++);
}
bool dinic_bfs(){
    memset(dist, 255, sizeof (dist));
    dist[src] = 0;
    int sizeQ = 0;
    Q[sizeQ++] = src;
    for (int cl = 0; cl < sizeQ; cl++)
        for (int k = Q[cl], i = head[k]; i >= 0; i = next1[i])
            if (flow[i] < capa[i] && dist[point[i]] < 0){
                dist[point[i]] = dist[k] + 1;
                Q[sizeQ++] = point[i];
            }
    return dist[dest] >= 0;
}
int dinic_dfs(int x, int exp){
    if (x == dest) return exp;
    for (int &i = work[x]; i >= 0; i = next1[i]){
        int v = point[i], tmp;
        if (flow[i] < capa[i] && dist[v] == dist[x] + 1 && (tmp = dinic_dfs(v, min(exp, capa[i] - flow[i]))) > 0){
            flow[i] += tmp;
            flow[i^1] -= tmp;
            return tmp;
        }
    }
    return 0;
}
int dinic_flow(){
    int result = 0;
    while (dinic_bfs()){
        for (int i = 0; i < node; i++) work[i] = head[i];
        while (1){
            int delta = dinic_dfs(src, oo);
            if (delta == 0) break;
            result += delta;
        }
    }
    return result;
}
//建图前,运行一遍init()；
//加边时，运行addedge(a,b,c,0),表示点a到b流量为c的边建成（注意点序号要从0开始）
//求解最大流运行dinic_flow(),返回值即为答案


int main()
{
while(scanf("%d%d",&n,&m)!=EOF)
{
int i,j;
int ta,tb,tc,td,sum=0;;
init(n+2,0,n+1);
memset(c,0,sizeof(c));
for(i=1;i<=m;i++)
{
scanf("%d%d%d%d",&ta,&tb,&tc,&td);
lo[i]=tc;
addedge(ta,tb,td-tc,0);
c[ta]-=tc;
c[tb]+=tc;
}
for(i=1;i<=n;i++)
{
if(c[i]>0)
{
addedge(0,i,c[i],0);
sum+=c[i];
}
else if(c[i]<0)
addedge(i,n+1,-c[i],0);
}
int ans;
ans=dinic_flow();
if(ans==sum)
{
printf("YES\n");
for(i=0;i<m;i++)
printf("%d\n",flow[i*2]+lo[i+1]);
}
else
printf("NO\n");
}
return 0;
}