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| #include <cstdio>
#include <string>
#include <cstring>
#include <vector>
#include <algorithm>
#include <map>
#include <set>
#include <functional>
#include <queue>
#include <cmath>
#include <cstdlib>
using namespace std;
typedef long long ll;
typedef pair<int , int > pii;
typedef unsigned long long ull;
namespace FastIO
{
template<typename T> inline T read(T& x) {
x = 0;
int f = 1;
char ch;
while (!isdigit(ch = getchar())) if (ch == '-') f = -1;
while (isdigit(ch)) x = (x << 1) + (x << 3) + (ch ^ 48), ch = getchar();
x *= f;
return x;
}
template<typename T, typename... Args> inline void read(T& x, Args &...x_) {
read(x);
read(x_...);
return;
}
inline ll read() {
ll x;
read(x);
return x;
}
};
using namespace FastIO;
template<int N, int M>
class Graph {
private :
struct Edge {
int fr, to, nt;
ll wt, fl, cp;
Edge() {}
Edge(int fr, int to, int nt, ll wt, ll cp, ll fl) :
fr(fr), to(to), nt(nt), wt(wt), cp(cp), fl(fl) {}
}e[M];
int hd[N], cnte;
public :
inline void clear() { memset(hd, 0, sizeof(hd)), cnte = 0; }
inline void AddEdge(int u, int v, ll w = 0, ll c = 0, ll f = 0) {
e[++cnte] = Edge(u, v, hd[u], w, c, f);
hd[u] = cnte;
}
inline int head(int u) { return hd[u]; }
inline int fr(int u) { return e[u].fr; }
inline int nt(int u) { return e[u].nt; }
inline int to(int u) { return e[u].to; }
inline ll wt(int u) { return e[u].wt; }
inline ll& flw(int u) { return e[u].fl; }
inline ll& cap(int u) { return e[u].cp; }
};
const int MaxV = 2010;
const int MaxE = 40010;
const ll INF = 1e18;
int n, m;
Graph< MaxV, MaxE >G;
inline void Input() {
read(n, m);
int u, v, c;
for(int i = 1; i <= m; i++) {
read(u, v, c);
G.AddEdge(u, v, c, 1);
G.AddEdge(v, u,-c, 0);
G.AddEdge(v, u, c, 1);
G.AddEdge(u, v,-c, 0);
}
}
ll dis[MaxV];
int path[MaxV], vis[MaxV];
inline bool SPFA(int S, int T, int nodenum) {
queue<int >q;
memset(vis, 0, sizeof(vis));
memset(path,-1,sizeof(path));
for(int i = 0; i <= nodenum; i++) dis[i] = INF;
vis[S] = 1, dis[S] = 0; q.push(S);
while(!q.empty()) {
int u = q.front(); q.pop();
vis[u] = 0;
for(int i = G.head(u); i; i = G.nt(i)) {
int v = G.to(i);
if(G.cap(i) && dis[v] > dis[u] + G.wt(i)) {
dis[v] = dis[u] + G.wt(i);
path[v] = i;
if(!vis[v]) {
q.push(v);
vis[v] = 1;
}
}
}
}
if(dis[T] == INF) return false;
return true;
}
inline pair<ll, ll> mcmf(int S, int T, int nodenum) {
ll flow = 0, minflow, mincost = 0;
while(SPFA(S, T, nodenum)) {
minflow = INF + 1;
for(int i = path[T]; i != -1; i = path[G.fr(i)]) {
minflow = min(minflow, G.cap(i));
}
flow += minflow;
for(int i = path[T]; i != -1; i = path[G.fr(i)]) {
G.cap(i) -= minflow;
G.cap(((i-1)^1)+1) += minflow;
}
mincost += dis[T] * minflow;
}
return make_pair(mincost, flow);
}
inline void Work() {
G.AddEdge(n + 1, 1, 0, 2);
G.AddEdge(1, n + 1, 0, 0);
G.AddEdge(n, n + 2, 0, 2);
G.AddEdge(n + 2, n, 0, 0);
printf("%lld\n", mcmf(n + 1, n + 2, n + 2).first);
}
int main() {
int T = 1;
while(T--) {
Input();
Work();
}
return 0;
}
|
