SPFA版本:
#include<bits/stdc++.h>
using namespace std;
namespace SPFA_Mincost_Maxflow {
const int MAXN=10000;
const int MAXM=100000;
const int INF=0x3f3f3f3f;
struct Edge {
int to,next,cap,flow,cost;
} edge[MAXM];
int head[MAXN],tol;
int pre[MAXN],dis[MAXN];
bool vis[MAXN];
void init() {
tol=0;
memset(head,-1,sizeof(head));
}
void add_edge(int u,int v,int cap,int cost) {
edge[tol].to=v;
edge[tol].cap=cap;
edge[tol].cost=cost;
edge[tol].flow=0;
edge[tol].next=head[u];
head[u]=tol++;
edge[tol].to=u;
edge[tol].cap=0;
edge[tol].cost=-cost;
edge[tol].flow=0;
edge[tol].next=head[v];
head[v]=tol++;
}
bool spfa(int s,int t) {
queue<int> q;
memset(dis,INF,sizeof(dis));
memset(vis,false,sizeof(vis));
memset(pre,-1,sizeof(pre));
dis[s]=0;
vis[s]=true;
q.push(s);
while(!q.empty()) {
int u=q.front();
q.pop();
vis[u]=false;
for(int i=head[u]; i!=-1; i=edge[i].next) {
int v=edge[i].to;
if(edge[i].cap>edge[i].flow&&dis[v]>dis[u]+edge[i].cost) {
dis[v]=dis[u]+edge[i].cost;
pre[v]=i;
if(!vis[v]) {
vis[v]=true;
q.push(v);
}
}
}
}
if(pre[t]==-1)
return false;
else
return true;
}
int mincost,maxflow;
void mincost_maxflow(int s,int t) {
int cost=0,flow=0;
while(spfa(s,t)) {
int tp=INF;
for(int i=pre[t]; i!=-1; i=pre[edge[i^1].to]) {
if(tp>edge[i].cap-edge[i].flow)
tp=edge[i].cap-edge[i].flow;
}
for(int i=pre[t]; i!=-1; i=pre[edge[i^1].to]) {
edge[i].flow+=tp;
edge[i^1].flow-=tp;
cost+=edge[i].cost*tp;
}
flow+=tp;
}
mincost=cost;
maxflow=flow;
return;
}
}
using namespace SPFA_Mincost_Maxflow;
int main() {
int N,M,S,T;
scanf("%d%d%d%d",&N,&M,&S,&T);
init();
while(M--) {
int u,v,cap,cost;
scanf("%d%d%d%d",&u,&v,&cap,&cost);
add_edge(u,v,cap,cost);
}
mincost_maxflow(S,T);
printf("%d %d\n",maxflow,mincost);
}
Dijkstra版本:
这个版本不容易被卡,据说会快70%。缺点是要控制负数费用不能负得太离谱,不然换 long long 试试吧。