http://acm.hdu.edu.cn/showproblem.php?pid=2255
km模板,二分图最优匹配,复杂度O(n^3)
http://www.cnblogs.com/jackge/archive/2013/05/03/3057028.html
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
#include <iostream> #include <cstdio> #include <cstring> using namespace std; const int N=310; const int INF=0x3f3f3f3f; int n,nx,ny; int linker[N],lx[N],ly[N],slack[N]; int visx[N],visy[N],w[N][N]; int DFS(int x) { visx[x]=1; for(int y=1;y<=ny;y++){ if(visy[y]) continue; int tmp=lx[x]+ly[y]-w[x][y]; if(tmp==0){ visy[y]=1; if(linker[y]==-1 || DFS(linker[y])){ linker[y]=x; return 1; } }else if(slack[y]>tmp){ slack[y]=tmp; } } return 0; } int KM() { int i,j; memset(linker,-1,sizeof(linker)); memset(ly,0,sizeof(ly)); for(i=1;i<=nx;i++) for(j=1,lx[i]=-INF;j<=ny;j++) if(w[i][j]>lx[i]) lx[i]=w[i][j]; for(int x=1;x<=nx;x++){ for(i=1;i<=ny;i++) slack[i]=INF; while(1){ memset(visx,0,sizeof(visx)); memset(visy,0,sizeof(visy)); if(DFS(x)) break; int d=INF; for(i=1;i<=ny;i++) if(!visy[i] && d>slack[i]) d=slack[i]; for(i=1;i<=nx;i++) if(visx[i]) lx[i]-=d; for(i=1;i<=ny;i++) if(visy[i]) ly[i]+=d; else slack[i]-=d; } } int res=0; for(i=1;i<=ny;i++) if(linker[i]!=-1) res+=w[linker[i]][i]; return res; } int main() { while(~scanf("%d",&n)) { nx=ny=n; for(int i=1;i<=n;i++) for(int j=1;j<=n;j++) scanf("%d",&w[i][j]); int ans=KM(); printf("%d\n",ans); } return 0; }