BZOJ 1324: Exca王者之剑 最小割+黑白染色
注意:在最小割轻易不要连流量为无穷大的双向边(这就意味着这两个点必须属于一个集合里了)
code:
#include <bits/stdc++.h> #define N 10005 #define I(s) freopen(s".in","r",stdin) #define O(s) freopen(s".out","w",stdout) #define setIO(s) I(s) const int dx[]={-1,0,1,0}; const int dy[]={0,1,0,-1}; using namespace std; const int INF=200000; const int inf=2000000001; namespace net { struct Edge { int u,v; int c; Edge(int u=0,int v=0,int c=0):u(u),v(v),c(c){} }; queue<int>q; vector<Edge>edges; vector<int>G[N]; int vv[N],vis[N],d[N],bo[N],s,t; void add(int u,int v,int c) { edges.push_back(Edge(u,v,c)); edges.push_back(Edge(v,u,0)); int o=edges.size(); G[u].push_back(o-2); G[v].push_back(o-1); } int dfs(int x,int cur) { if(x==t) return cur; int an=0,flow=0; for(int i=vv[x];i<G[x].size();++i,++vv[x]) { Edge e=edges[G[x][i]]; if(e.c>0&&d[e.v]==d[x]+1) { an=dfs(e.v,min(cur,e.c)); if(an) { cur-=an; flow+=an; edges[G[x][i]].c-=an; edges[G[x][i]^1].c+=an; if(!cur) break; } } } return flow; } int bfs() { memset(vis,0,sizeof(vis)); d[s]=0; vis[s]=1; q.push(s); while(!q.empty()) { int u=q.front(); q.pop(); for(int i=0;i<G[u].size();++i) { if(edges[G[u][i]].c>0) { int v=edges[G[u][i]].v; if(!vis[v]) { vis[v]=1; d[v]=d[u]+1; q.push(v); } } } } return vis[t]; } int maxflow() { int re=0; while(bfs()) { memset(vv,0,sizeof(vv)); re+=(int)dfs(s,inf); } return re; } }; int n,m,a[103][103],id[103][103]; int main() { // setIO("input"); scanf("%d%d",&n,&m); int SUM=0,tim=0; for(int i=1;i<=n;++i) for(int j=1;j<=m;++j) scanf("%d",&a[i][j]),SUM+=a[i][j],id[i][j]=++tim; int s=0,t=id[n][m]+2; net::s=s,net::t=t; for(int i=1;i<=n;++i) { for(int j=1;j<=m;++j) { if((i+j)&1) { net::add(s,id[i][j],a[i][j]); for(int k=0;k<4;++k) { int X=i+dy[k],Y=j+dx[k]; if(X>=1&&X<=n&&Y>=1&&Y<=m) { net::add(id[i][j],id[X][Y],10000); } } } else net::add(id[i][j],t,a[i][j]); } } printf("%d\n",SUM-net::maxflow()); return 0; }