版权声明:转载请声明出处,谢谢配合。 https://blog.csdn.net/zxyoi_dreamer/article/details/81874107
参考题目:loj101
解析:
什么时候有时间什么时候更新系列。。。
代码:
#include<bits/stdc++.h>
using namespace std;
#define re register
#define ll long long
#define ull unsigned long long
#define itn int
#define gc getchar
#define il inline
il
ll getint(){
ll num=0;
char c=gc();
for(;!isdigit(c);c=gc());
for(;isdigit(c);c=gc())num=(num<<1)+(num<<3)+(c^48);
return num;
}
il
void outint(const ll &a){
if(a<0)return putchar('-'),outint(-a);
if(a>9)outint(a/10);
putchar((a%10)^48);
}
int n,m;
int Last[105],nxt[10005],to[10005],ecnt=1;
ll cap[10005];
il
void addedge(int u,int v ,ll val){
nxt[++ecnt]=Last[u],Last[u]=ecnt,to[ecnt]=v,cap[ecnt]=val;
nxt[++ecnt]=Last[v],Last[v]=ecnt,to[ecnt]=u,cap[ecnt]=0;
}
int s=1,t,lev[205],cur[205];
il
bool BFS(){
queue<int> q;
fill(lev,lev+n+1,-1);
for(int re i=1;i<=n;++i)cur[i]=Last[i];
q.push(s),lev[s]=0;
while(!q.empty()){
int u=q.front();
q.pop();
for(int re e=Last[u],v=to[e];e;e=nxt[e],v=to[e]){
if(cap[e]&&lev[v]==-1){
lev[v]=lev[u]+1;
if(v==t)return true;
q.push(v);
}
}
}
return false;
}
il
ll Dinic(const int &u,const ll &flow){
if(u==t)return flow;
ll ans=0;
for(int &e=cur[u],v=to[e];e;e=nxt[e],v=to[e]){
if(cap[e]>0&&lev[u]<lev[v]){
ll delta=Dinic(v,min((long long)cap[e],flow-ans));
if(delta){
cap[e]-=delta;
cap[e^1]+=delta;
ans+=delta;
if(ans==flow)break;
}
}
}
if(ans!=flow)lev[u]=-1;
return ans;
}
il
ll maxflow(){
ll ans=0;
while(BFS())ans+=Dinic(s,(1ll<<61));
return ans;
}
int main(){
n=getint();
m=getint();
s=getint();
t=getint();
for(int re i=1;i<=m;++i){
int u=getint(),v=getint();
ll w=getint();
addedge(u,v,w);
}
outint(maxflow());
putchar('\n');
return 0;
}