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图论-最大流-Ford-Fulkerson模板.cpp
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图论-最大流-Ford-Fulkerson模板.cpp
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#include<bits/stdc++.h>
#define per(i,a,b) for(int i = (a);i <= (b);++i)
#define rep(i,a,b) for(int i = (a);i >= (b);--i)
using namespace std;
#define INF 0x3f3f3f3f
const int maxn = 1e5;
int n = 0,m = 0;
int s = 0,t = 0;
struct edge{
int to,cap,rev;
};
vector<edge> g[maxn+10];
bool vis[maxn+10];
void add_edge(int from,int to,int cap){
g[from].push_back(edge{to,cap,g[to].size()});//记录反向边在终点的位置,也就是下面to增加一条边的位置
g[to].push_back(edge{from,0,g[from].size()-1});//反向边,后面是from的位置
}
int dfs(int s,int t,int f){
if(s == t){
return f;
}
vis[s] = true;
int size = g[s].size();
per(i,0,size-1){
edge& e = g[s][i];
if(!vis[e.to] && e.cap > 0){
int d = dfs(e.to,t,min(f,e.cap));
if(d > 0){
e.cap -= d;
g[e.to][e.rev].cap += d;
return d;
}
}
}
return 0;
}
int max_match(int s,int t){
int flow = 0;
while(true){
memset(vis,false,sizeof(vis));
int f = dfs(s,t,INF);
if(f == 0){
return flow;
}
flow += f;
}
return -1;
}
int main(){
while(~scanf("%d %d",&n,&m)){
per(i,1,m){
int x = 0,y = 0,z = 0;
scanf("%d %d %d",&x,&y,&z);
add_edge(x,y,z);
}
scanf("%d %d",&s,&t);
int ans = max_match(s,t);
}
return 0;
}