luogu P4013 数字梯形问题 网络流24 最大费用最大流
#include<cstdio> #include<cstring> #include<algorithm> #include<queue> #include<iostream> using namespace std; const int maxn=100010; bool vis[maxn]; int n,m,s,t,x,y,z,f,cost[maxn],pre[maxn],last[maxn],flow[maxn],maxflow,mincost; //cost最小花费;pre每个点的前驱;last每个点的所连的前一条边;flow源点到此处的流量 //maxflow 最大流量 //mincost 最大流量的情况下的最小花费 struct Edge { int to,next,flow,cost;//flow流量 cost花费 } edge[maxn]; int head[maxn],num_edge; queue <int> q; int mp[1001][1001],id[1001][1001],cnt; const int inf=0x3f3f3f3f; void add(int from,int to,int flow,int cost) { edge[++num_edge].next=head[from]; edge[num_edge].to=to; edge[num_edge].flow=flow; edge[num_edge].cost=cost; head[from]=num_edge; edge[++num_edge].next=head[to]; edge[num_edge].to=from; edge[num_edge].flow=0; edge[num_edge].cost=-cost; head[to]=num_edge; } bool spfa(int s,int t) { memset(cost,0x3f,sizeof(cost)); memset(flow,0x3f,sizeof(flow)); memset(vis,0,sizeof(vis)); q.push(s); vis[s]=1; cost[s]=0; pre[t]=-1; while (!q.empty()) { int now=q.front(); q.pop(); vis[now]=0; for (int i=head[now]; i!=-1; i=edge[i].next) { if (edge[i].flow>0 && cost[edge[i].to]>cost[now]+edge[i].cost)//正边 { cost[edge[i].to]=cost[now]+edge[i].cost; pre[edge[i].to]=now; last[edge[i].to]=i; flow[edge[i].to]=min(flow[now],edge[i].flow);// if (!vis[edge[i].to]) { vis[edge[i].to]=1; q.push(edge[i].to); } } } } return pre[t]!=-1; } void MCMF() { while (spfa(s,t)) { int now=t; maxflow+=flow[t]; mincost+=cost[t]*flow[t]; while (now!=s) { //从源点一直回溯到汇点 edge[last[now]].flow-=flow[t];//flow和cost容易搞混 edge[last[now]^1].flow+=flow[t]; now=pre[now]; } } } int main() { memset(head,-1,sizeof(head)); num_edge=1; cin>>n>>m; cnt=1; for(int i=1; i<=m; i++) for(int j=1; j<=n+i-1; j++) { cin>>mp[i][j]; id[i][j]=++cnt; } s=0,t=1; int T=cnt; for(int i=1; i<=m; i++) for(int j=1; j<=n+i-1; j++) { add(id[i][j],id[i][j]+T,1,-mp[i][j]);//建反向的 if(i==m) continue; add(id[i][j]+T,id[i+1][j],1,0); add(id[i][j]+T,id[i+1][j+1],1,0); } for(int i=1; i<=n; i++) add(s,id[1][i],1,0); for(int i=1; i<=n+m-1; i++) add(id[m][i]+T,t,1,0); MCMF(); cout<<-mincost<<endl;//输出负数 for(int i=2; i<=num_edge; i+=2) edge[i].flow+=edge[i^1].flow,edge[i^1].flow=0; maxflow=mincost=0; for(int i=1; i<=m; i++) for(int j=1; j<=n+i-1; j++) { add(id[i][j],id[i][j]+T,inf,-mp[i][j]); } for(int i=1; i<=n+m-1; i++) add(id[m][i]+T,t,inf,0); MCMF(); cout<<-mincost<<endl; for(int i=2; i<=num_edge; i+=2) edge[i].flow+=edge[i^1].flow,edge[i^1].flow=0; maxflow=mincost=0; for(int i=1; i<=m-1; i++) for(int j=1; j<=n+i-1; j++) { add(id[i][j]+T,id[i+1][j],inf,0); add(id[i][j]+T,id[i+1][j+1],inf,0); } MCMF(); cout<<-mincost<<endl; return 0; }