可行流

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <queue>
#define inf (1 << 28)
using namespace std;
const int maxn = 300,maxm=1e5+1e2;
//前向星
struct node{
    int to,val,lid,pre;
}e[maxm];
int id[maxn],cnt = 0;
//dinic
int cur[maxn];
int flor[maxn];//BFS的分层处理

int n,m;//基础变量

int upflow[maxn];//差流（可升流）
int retf[maxm];//结果
int low[maxm];//下界

void init()
{
    memset(id,-1,sizeof(id));
    memset(upflow,0,sizeof(upflow));
    cnt = 0;
}
//网络流加边
void add(int from,int to,int val,int lid)
{
    e[cnt].lid = lid;
    e[cnt].to = to;
    e[cnt].val = val;
    e[cnt].pre = id[from];
    id[from] = cnt++;
    swap(from,to);
    e[cnt].lid = lid;
    e[cnt].to = to;
    e[cnt].val = 0;
    e[cnt].pre = id[from];
    id[from] = cnt++;
}
//Dinic
//bfs分层
bool bfs(int s,int t)
{
    memset(flor,0,sizeof(flor));
    flor[s] = 1;
    queue<int> q;
    while(q.size())q.pop();
    q.push(s);

    while(q.size())
    {
        int now = q.front();
        q.pop();

        for(int i = id[now];~i;i = e[i].pre)
        {
            int to = e[i].to;
            int val = e[i].val;
            if(val > 0 && flor[to] == 0)
            {
                flor[to] = flor[now] + 1;
                //printf("%d flor = %d\n",to,flor[to]);
                q.push(to);
                if(to == t)return 1;
            }
        }
    }
    return 0;
}
int dfs(int s,int t,int value)
{
    //printf("s t value = ::: %d %d %d\n",s,t,value);
    if(s == t || value == 0)return value;
    int ret = value,a;
    for(int &i = cur[s];~i;i = e[i].pre)
    {
        int to = e[i].to;
        int val = e[i].val;
        //printf("to = %d val = %d flornow = %d florto = %d\n",to,val,flor[s],flor[to]);
        if(flor[to] == flor[s] + 1 && (a = dfs(to,t,min(ret,val))))
        {
            //printf("a = %d\n",a);
            e[i].val -= a;
            e[i^1].val += a;
            ret -= a;
            if(ret == 0)break;
        }
    }
    if(ret == value)flor[s] = 0;

    return value - ret;
}
int dinic(int s,int t)
{
    int ret = 0;
    while(bfs(s,t))
    {
        memcpy(cur,id,sizeof(id));
        ret += dfs(s,t,inf);
        //cout<<ret<<endl;
    }
    return ret;
}


int main()
{
    int T;
    scanf("%d",&T);
    int s,t;
    while(T--)
    {
        init();
        scanf("%d%d",&n,&m);
        s = 0;
        t = n + 1;
        int from,to,up;
        //附加流基础建图，表示基础流最大可扩充的容量
        for(int i = 1;i <= m;++i)
        {
            scanf("%d%d%d%d",&from,&to,&low[i],&up);
            add(from,to,up - low[i],i);
            upflow[from] -= low[i];
            upflow[to] += low[i];
            //printf("Line : %d - %d - %d\n",from,to,up-low[i]);
        }
        //补充流建边
        int sumf = 0;
        for(int i = 1;i <= n;++i)
        {
            if(upflow[i] < 0)//流入 < 流出
            {
                add(i,t,-upflow[i],0);
                //printf("Line : %d - %d - %d\n",i,t,-upflow[i]);
            }
            else//流入 > 流出
            {
                sumf += upflow[i];
                add(s,i,upflow[i],0);
                //printf("Line : %d - %d - %d\n",s,i,upflow[i]);
            }
        }
        if(dinic(s,t) == sumf)
        {
            printf("YES\n");
            for(int now = 1;now <= n;++now)
            {
                for(int i = id[now];~i;i = e[i].pre)
                {
                    int lid = e[i].lid;
                    // i % 2 == 0对应的是正向边
                    if(lid == 0 || i % 2 == 0)continue;
                    //printf("%d + %d === %d\n",low[lid],e[i].val,i);
                    retf[lid] = low[lid] + e[i].val;
                }

            }
            for(int i=1;i<=m;++i)printf("%d\n",retf[i]);
        }
        else
        {
            printf("NO\n");
        }
        if(T)printf("\n");
    }
    return 0;
}