cogs739. [网络流24题] 运输问题

739. [网络流24题] 运输问题

输入文件示例 输出文件示例
tran.in
2 3
220 280
170 120 210
77 39 105

150 186 122

tran.out

48500

69140

题解：

裸的费用流 spfa即可

代码：

#include <iostream>#include <cstdio>#include <cstring>#include <vector>#include <queue>using namespace std;const int maxn=200;const int maxm=200;const int inf=0x3f3f3f3f;int n,m;struct edge{int to,cap,cost,rev;};vector<edge> g[maxn];int a[maxn];int b[maxn];int p[maxm][maxn];int dis[maxn+maxm+2];int q[maxn+maxm+2];bool inque[maxn+maxm+2];int prevv[maxn+maxm+2];int preve[maxn+maxm+2];int aj[maxn+maxm+2];int ans=0;inline void addedge(int from,int to,int cap,int cost){g[from].push_back((edge){to,cap,cost,g[to].size()});g[to].push_back((edge){from,0,-cost,g[from].size()-1});}inline bool spfa(int st,int ed){memset(prevv,0,sizeof(prevv));memset(preve,0,sizeof(preve));memset(inque,false,sizeof(inque));memset(dis,inf,sizeof(dis));dis[st]=0;memset(q,0,sizeof(q));int head=0;int tail=0;q[head]=st;aj[st]=inf;inque[st]=true;while(head<=tail){int top=q[head];inque[top]=false;head++;for(unsigned i=0;i<g[top].size();i++){edge &e=g[top][i];if(dis[e.to]>dis[top]+e.cost && e.cap>0){aj[e.to]=min(e.cap,aj[top]);dis[e.to]=dis[top]+e.cost;prevv[e.to]=top;preve[e.to]=i;if(!inque[e.to]){tail++;q[tail]=e.to;inque[e.to]=true;}}}}if(dis[ed]==inf)return false;ans+=aj[ed]*dis[ed];for(int i=ed;i!=st;i=prevv[i]){edge &e=g[prevv[i]][preve[i]];e.cap-=aj[ed];g[e.to][e.rev].cap+=aj[ed];}return true;}int main(){freopen("tran.in","r",stdin);freopen("tran.out","w",stdout);scanf("%d%d",&m,&n);for(int i=1;i<=m;i++)scanf("%d",&a[i]);for(int i=1;i<=n;i++)scanf("%d",&b[i]);int s=0;int t=n+m+1;for(int i=1;i<=m;i++){addedge(s,i,a[i],0);}for(int i=1;i<=n;i++){addedge(i+m,t,b[i],0);}for(int i=1;i<=m;i++){for(int j=1;j<=n;j++){int cost;scanf("%d",&cost);p[i][j]=cost;}}for(int i=1;i<=m;i++){for(int j=1;j<=n;j++){addedge(i,j+m,inf,p[i][j]);}}while(spfa(s,t));printf("%d\n",ans);ans=0;for(int i=0;i<maxn;i++){g[i].clear();}for(int i=1;i<=m;i++){addedge(s,i,a[i],0);}for(int i=1;i<=n;i++){addedge(i+m,t,b[i],0);}for(int i=1;i<=m;i++){for(int j=1;j<=n;j++){addedge(i,j+m,inf,-p[i][j]);}}while(spfa(s,t));printf("%d\n",-ans);return 0;}