无源汇有上下界的网络流模板

例题： LOJ115：https://loj.ac/problem/115

Dinic实现。。。。。sap不会写。。/(ㄒoㄒ)/~~

模板自用：

#include <iostream>
#include <cstdio>
#include <cstring>
#include <queue>
#include <cmath>
#include <algorithm>
#define mem(a,b) memset(a,b,sizeof(a))
using namespace std;
const int maxn = 100102, INF = 0x7fffffff;
int d[maxn], head[maxn], in[maxn], low[maxn], id[maxn];
int n, m, s, t, ans_flow, ans;
struct node{
    int u, v, c, f, next;
}Node[2*maxn];

void add(int u, int v, int c, int f,int i)
{
    Node[i].u = u;
    Node[i].v = v;
    Node[i].c = c;
    Node[i].f = f;
    Node[i].next = head[u];
    head[u] = i;
}
int bfs()
{
    queue<int> Q;
    mem(d,0);
    Q.push(s);
    d[s] = 1;
    while(!Q.empty())
    {
        int u = Q.front(); Q.pop();
        for(int i=head[u]; i!=-1; i=Node[i].next)
        {
            node e = Node[i];
            if(!d[e.v] && e.c  > e.f)
            {
                d[e.v] = d[e.u] + 1;
                Q.push(e.v);
            }
        }
    }
    return d[t] != 0;
}

int dfs(int u, int cap)
{
    if(u == t)
        return cap;
    for(int i=head[u]; i!=-1; i=Node[i].next)
    {
        node e = Node[i];
        if(d[e.v] == d[u] + 1 && e.c > e.f)
        {
            int V = dfs(e.v, min(cap, e.c - e.f));
            if(V > 0)
            {
                Node[i].f += V;
                Node[i^1].f -= V;
                return V;
            }
        }
    }
    return 0;
}

int Dinic()
{
    int sum_flow = 0;
    while(bfs()){
        while(int l = dfs(0,INF))
            sum_flow += l;
    }
    return sum_flow;
}

int main()
{
    while(cin>> n >> m)
    {
        ans = 0;
        mem(head,-1);
        ans_flow = 0;
        int cnt = 0;
        mem(in,0);
        s = 0; t = n+1;
        for(int i=0; i<m; i++)
        {
            int u, v, b, d;
            cin>> u >> v >> b >> d;
            id[i] = cnt;
            add(u,v,d-b,0,cnt++);
            add(v,u,0,0,cnt++);
            in[v] += b;
            in[u] -= b;
            low[i] = b;
        }
        for(int i=1; i<=n; i++)
        {
            if(in[i] > 0)
            {
                ans_flow += in[i];
                add(s,i,in[i],0,cnt++);
                add(i,s,0,0,cnt++);
            }
            else
            {
                add(i,t,-in[i],0,cnt++);
                add(t,i,0,0,cnt++);
            }
        }
        int sum_flow = Dinic();
        if(sum_flow == ans_flow){
            cout<< "YES" <<endl;
            for(int i=0; i<m; i++)
                cout<< low[i] + Node[id[i]^1].c - Node[id[i]^1].f  <<endl;
        }
        else
            cout<< "NO" <<endl;
    }
    return 0;
}