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| #include<bits/stdc++.h>
#define RG register
#define file(x) freopen(#x".in", "r", stdin);freopen(#x".out", "w", stdout);
#define clear(x, y) memset(x, y, sizeof(x));
using namespace std;
inline int read()
{
int data=0, w=1;
char ch=getchar();
while(ch!='-'&&(ch<'0'||ch>'9')) ch=getchar();
if(ch=='-') w=-1, ch=getchar();
while(ch>='0'&&ch<='9') data=(data<<3)+(data<<1)+(ch^48), ch=getchar();
return data*w;
}
const int maxn(10010), maxm(1e5+10), I(2147483647);
int n, m, s, t;
struct edge { int next, to, cap; } e[maxm << 1];
int head[maxn], e_num, q[maxn], tail, lev[maxn], cur[maxn];
inline void add_edge(int from, int to, int cap)
{
e[e_num]={head[from], to, cap};
head[from]=e_num++;
}
inline void add(int from, int to, int cap) { add_edge(from, to, cap); add_edge(to, from, 0); }
inline bool bfs()
{
clear(lev, 0);
q[tail=lev[s]=1]=s;
for(RG int i=1;i<=tail;i++)
{
int x=q[i];
for(RG int j=head[x];~j;j=e[j].next)
{
int to=e[j].to;
if(lev[to] || (!e[j].cap)) continue;
q[++tail]=to; lev[to]=lev[x]+1;
}
}
return lev[t];
}
int dfs(int x, int f)
{
if(x==t) return f;
int ans=0, cap;
for(RG int &i=cur[x];~i;i=e[i].next)
{
int to=e[i].to;
if(e[i].cap && lev[to]==lev[x]+1)
{
cap=dfs(to, min(f-ans, e[i].cap));
e[i].cap-=cap;
e[i^1].cap+=cap;
ans+=cap;
if(ans==f) break;
}
}
return ans;
}
inline int dinic()
{
RG int ans=0;
while(bfs())
{
for(RG int i=1;i<=n;i++) cur[i]=head[i];
ans+=dfs(s, I);
}
return ans;
}
int fr, to, c;
int main()
{
clear(head, -1);
n=read(); m=read(); s=read(); t=read();
for(RG int i=1;i<=m;i++) fr=read(), to=read(), c=read(), add(fr, to, c);
return printf("%d\n", dinic())&0;
}
|