@[极冬寒雪](/user/413020)
```cpp
#include<cstdio>
#include<cstring>
#include<queue>
#define int long long
using namespace std;
int re()
{
int s=0,f=1;char ch=getchar();
while(ch>'9'||ch<'0')
{
if(ch=='-')f=-1;
ch=getchar();
}
while(ch>='0'&&ch<='9')
s=s*10+ch-48,ch=getchar();
return s*f;
}
void wr(int s)
{
if(s<0)putchar('-'),s=-s;
if(s>9)wr(s/10);
putchar(s%10+48);
}
const int N=207,M=5007;
int n,m,s,t,ans;
int fir[N],nex[M<<1],poi[M<<1],val[M<<1],cnt=1;
int arc[N];
void ins(int x,int y,int z)
{
nex[++cnt]=fir[x];
poi[cnt]=y;
val[cnt]=z;
fir[x]=cnt;
}
int dep[N];
bool bfs()
{
queue<int>h;
for(int i=1;i<=n;i++)
dep[i]=2147483647,arc[i]=fir[i];
dep[s]=0;h.push(s);
while(h.size())
{
int now=h.front();h.pop();
for(int i=fir[now];i;i=nex[i])
{
int p=poi[i];
if(val[i]==0)continue;
if(dep[p]==2147483647)
{
dep[p]=dep[now]+1;
h.push(p);
}
}
}
return dep[t]!=2147483647;
}
int dfs(int now,int minn)
{
if(now==t)
return minn;
int sum=0,ff;
for(int i=arc[now];i;i=nex[i])
{
arc[now]=i;int p=poi[i];
if(val[i]==0||dep[p]!=dep[now]+1)continue;
ff=dfs(p,min(minn,val[i]));
val[i]-=ff,val[i^1]+=ff;
sum+=ff;minn-=ff;
if(!minn) break;
}if(!sum) dep[now]=2147483647;
return sum;
}
signed main()
{
n=re();m=re();s=re();t=re();
for(int i=1;i<=m;i++)
{
int x=re(),y=re(),z=re();
ins(x,y,z),ins(y,x,0);
}
while(bfs())
ans+=dfs(s,2147483647);
wr(ans);
return 0;
}
```
稍微改了下，应该是dfs的问题，其实不加当前弧优化也是能过的。
[不加当前弧优化](https://www.luogu.com.cn/record/82518364)
[加当前弧优化](https://www.luogu.com.cn/record/82518128)
by AIskeleton @ 2022-08-05 10:46:46
@[A_I_Skeleton](/user/540715) 谢谢dalao，A 了/qq
by Zvelig1205 @ 2022-08-05 11:03:34