网络流sap

#include<bits/stdc++.h>
#define maxn 12005
#define maxm 240055	
#define inf 0x3f3f3f3f
using namespace std;

int n,m,S,T;
int buf[maxn],info[maxn],Prev[maxm],to[maxm],cap[maxm],cnt_e=1;
void Node(int u,int v,int c){ Prev[++cnt_e]=info[u],info[u]=cnt_e,to[cnt_e]=v,cap[cnt_e]=c; }
void Line(int u,int v,int c){ Node(u,v,c),Node(v,u,0); }

int h[maxn],gap[maxn];
int aug(int now,int Max)
{
	if(now == T) return Max;
	int inc , st = Max;
	for(int &i=info[now];i;i=Prev[i])
		if(cap[i] && h[to[i]]+1 == h[now])
		{	
			inc = aug(to[i] , min(cap[i] , st));
			cap[i] -= inc , cap[i^1] += inc;
			if((st-=inc) == 0){ /*info[now]=buf[now];此句加了相当于没有加当前弧优化，不需要，但是注意出去还要用info的时候memcpy回来*/ return Max;}
		}
	if(!(--gap[h[now]])) h[S] = n + 1;
	++gap[++h[now]];info[now]=buf[now];
	return Max - st;
}

int sap()
{
	int stm = 0;
	memset(h,0,sizeof h);
	memset(gap,0,sizeof gap);
	memcpy(buf,info,sizeof info);
	for(;h[S] <= n;)
		stm += aug(S,inf);
	return stm;
}

int main()
{
	scanf("%d%d%d%d",&n,&m,&S,&T);
	for(int i=1;i<=m;i++)
	{
		int u,v,w;
		scanf("%d%d%d",&u,&v,&w);
		Line(u,v,w);
	}
	printf("%d\n",sap());
}