网络流最小费用流模板
#include<cstdio>
#include<vector>
#include<queue>
#include<algorithm>
#include<cstring>
#define REP(i, a, b) for(int i = (a); i < (b); i++)
using namespace std;
typedef long long ll;
const int MAXN = 4123;
struct Edge
{
int from, to, cap, flow, cost;
Edge(int from, int to, int cap, int flow, int cost) : from(from), to(to), cap(cap), flow(flow), cost(cost) {};
};
vector<Edge> edges;
vector<int> g[MAXN];
int p[MAXN], a[MAXN], d[MAXN], vis[MAXN], n, m, s, t;
void AddEdge(int from, int to, int cap, int cost)
{
edges.push_back(Edge(from, to, cap, 0, cost));
edges.push_back(Edge(to, from, 0, 0, -cost));
g[from].push_back(edges.size() - 2);
g[to].push_back(edges.size() - 1);
}
bool spfa(int& flow, ll& cost) //开longlong防炸
{
REP(i, 0, t + 1) d[i] = (i == s ? 0 : 1e9);
memset(vis, 0, sizeof(vis));
a[s] = 1e9; vis[s] = 1; p[s] = 0;
queue<int> q;
q.push(s);
while(!q.empty())
{
int u = q.front(); q.pop();
vis[u] = 0;
REP(i, 0, g[u].size())
{
Edge& e = edges[g[u][i]];
if(e.cap > e.flow && d[e.to] > d[u] + e.cost)
{
d[e.to] = d[u] + e.cost;
p[e.to] = g[u][i];
a[e.to] = min(a[u], e.cap - e.flow);
if(!vis[e.to]) { vis[e.to] = 1; q.push(e.to); }
}
}
}
if(d[t] == 1e9) return false;
flow += a[t]; //加的是a数组
cost += d[t] * a[t];
for(int u = t; u != s; u = edges[p[u]].from)
{
edges[p[u]].flow += a[t]; //注意区分a数组和d数组,a数组是流量,d数组是费用
edges[p[u] ^ 1].flow -= a[t];
}
return true;
}
int mincost(ll& cost)
{
int flow = 0; cost = 0;
while(spfa(flow, cost));
return flow;
}
int main()
{
//输入略
ll ans;
mincost(ans);
printf("%lld\n", ans);
return 0;
}