最大流模板（洛谷3376）

#include<iostream>#include<cstdio>#include<cstdlib>#include<cstring>#include<cmath>#include<algorithm>#define rep(i,a,b) for(register int i=a;i<=b;i++)#define dep(i,a,b) for(register int i=a;i>=b;i--)#define reg(x) for(int i=last[x];i;i=e[i].next)#define ll long long#define mem(x,num) memset(x,num,sizeof(x))#define inf 1844387848using namespace std;inline ll read(){    ll f=1,x=0;char ch=getchar();    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}    while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}    return x*f;}const int maxn=1e5+6,maxq=1e6+6;struct edge{ll to,from,v,t,next;}e[maxn<<1];ll n,m,k,cnt=1,ans,s,t,last[maxn],que[maxq],h[maxq];bool bfs(){    ll head=0,tail=0,now;    mem(h,-1);que[0]=s,h[s]=0;    while(head<=tail){        now=que[head++];        reg(now)            if(e[i].v&&h[e[i].to]==-1){h[e[i].to]=h[now]+1;que[++tail]=e[i].to;}    }    if(h[t]==-1)return 0;else return 1;}int dfs(int x,int f){    if(x==t)return f;    ll w,used=0;    reg(x)        if(e[i].v&&h[e[i].to]==h[x]+1){            w=f-used;w=dfs(e[i].to,min(w,e[i].v));            e[i].v-=w;e[i^1].v+=w;            used+=w;if(used==f)return f;        }    if(!used)h[x]=-1;    return used;}void dinic(){while(bfs())ans+=dfs(s,inf);}int main(){     n=read(),m=read(),s=read(),t=read();    rep(i,1,m){        ll u=read(),v=read(),w=read();        e[++cnt]=(edge){v,u,w,w,last[u]};last[u]=cnt;        e[++cnt]=(edge){u,v,0,-w,last[v]};last[v]=cnt;    }    dinic();    cout<<ans<<endl;    return 0;}