HDU6214 Smallest Minimum Cut 【最大流求最小割边】

#include<stdio.h>
#include<bits/stdc++.h>
#define ll long long
#define pii pair<int,int>
#define pll pair<ll,ll>
#define MEM(a,x) memset(a,x,sizeof(a))
#define lowbit(x) ((x)&-(x))

using namespace std;

const int INF = 1e9+7;
const int inf=INF;

const int N = 250 + 5;//点数
const int M = 2e3 + 50;//边数*2（包括反向边）

int level
;//标号 level[i]:s到i的最短距离

struct Edge{
int to,c,next;
}edge[M];
int head
;

inline void add_edge(int k,int u,int v,int c){
edge[k].to = v;
edge[k].c = c;
edge[k].next = head[u];
head[u] = k;
}

bool bfs(int s,int t,int n){//标号 计算level
deque<int>que;
fill(level,level+n+1,-1);
que.push_back(s);
level[s] = 0;
while(!que.empty()){
int u = que.front();
if(u == t){
return true;
}
que.pop_front();
for(int i = head[u];i!=-1;i = edge[i].next){
if(edge[i].c > 0 && level[edge[i].to] == -1){
level[edge[i].to] = level[u] + 1;
que.push_back(edge[i].to);
}
}
}
return false;
}

int dfs(int u,int t,int maxf){//u：所在的点 t：汇点 maxf：能流到u的流量
if(u == t){
return maxf;
}
int sum = 0;
for(int i = head[u];i!=-1;i = edge[i].next){
Edge&e = edge[i];
if(e.c>0 && level[e.to]>level[u]){
int f = dfs(e.to,t,min(maxf - sum,e.c));
sum += f;
edge[i].c -= f;
edge[i^1].c += f;
if(sum == maxf){//流量用完了
break;
}
}
}
level[u]=-1;
return sum;
}

int dinic(int s,int t,int n){//s:源点 t:汇点 n：点数
int ans = 0;
while(bfs(s,t,n)){
ans += dfs(s,t,INF);
}
return ans;
}

int slove(int n,int m){
fill(head,head+n+1,-1);
int S,T;
scanf("%d%d",&S,&T);
int nume=0;
for(int i=0;i<m;++i){
int u,v,w;
scanf("%d%d%d",&u,&v,&w);
add_edge(nume++,u,v,w*2000+1);
add_edge(nume++,v,u,0);
}
return dinic(S,T,n+1)%2000;
}

int main(){
//freopen("/home/lu/code/r.txt","r",stdin);
//freopen("/home/lu/code/w.txt","w",stdout);
int T;
scanf("%d",&T);
while(T--){
int n,m;
scanf("%d%d",&n,&m);
printf("%d\n",slove(n,m));
}
return 0;
}