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| #include <bits/stdc++.h>
#pragma optimization_level 3
#pragma GCC optimize("Ofast,no-stack-protector,unroll-loops,fast-math,O3")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx")
#pragma GCC optimize("Ofast")
#pragma GCC target("avx,avx2,fma")
#pragma GCC optimization ("unroll-loops")
#define MAX_N 505
#define ll long long
#define pll pair<ll, ll>
#define vpll vector<pll>
#define vll vector<ll>
#define vall3 vector<array<ll,3>>
#define vs vector<string>
#define vvll vector<vll>
#define all(a) begin(a), end(a)
using namespace std;
ll n,m;
vector<ll> adj[MAX_N];
ll path[MAX_N], cap[MAX_N][MAX_N], flo[MAX_N][MAX_N];
bool bfs(ll u, ll v) {
memset(path, 0, sizeof path);
queue<ll> q;
q.push(u);
while(!q.empty() and !path[v]) {
auto n = q.front(); q.pop();
for(auto& m : adj[n]) {
if(cap[n][m] - flo[n][m] > 0 and !path[m]) {
path[m] = n;
q.push(m);
}
}
}
return path[v] != 0;
}
ll solve(vall3& edges, ll u, ll v) {
for(auto& [u, v, w] : edges) {
adj[u].push_back(v);
adj[v].push_back(u);
cap[u][v] += w;
cap[v][u] += w;
flo[u][v] += w;
}
ll sum = 0;
while(bfs(u,v)) {
ll vv = v, mi = INT_MAX;
while(vv != u) {
auto uu = path[vv];
mi = min(mi, cap[uu][vv] - flo[uu][vv]);
vv = uu;
}
vv = v;
while(vv != u) {
auto uu = path[vv];
flo[uu][vv] += mi;
flo[vv][uu] -= mi;
vv = uu;
}
sum += mi;
}
return sum;
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cin>>n>>m;
ll u,v;
vall3 edges;
while(m--) {
cin>>v>>u;
edges.push_back({u,v,1});
}
cout<<solve(edges, 1,2);
return 0;
}
|
