HDU-2255-奔小康赚大钱（KM）

链接：http://acm.hdu.edu.cn/showproblem.php?pid=2255

二分图最大权匹配

//#pragma comment(linker, "/STACK:1024000000,1024000000")
#include <cstring>
#include <cstdio>
#include <algorithm>
#include <iostream>
#include <queue>
#include <cmath>
#include <string>
#include <map>
#include <stack>
using namespace std;
#define INF 0x3f3f3f3f
#define MAXN 5007
#define MAXM 5007
const int mod=499999;
#define eps 1e-8
const int N = 310;
int nx,ny,g[N][N];
int linker[N],lx[N],ly[N];
int slack[N];
bool visx[N],visy[N];
bool DFS(int x)
{
    visx[x]=1;
    for(int y=1; y<=ny; ++y)
    {
        if(visy[y])continue;
        int temp=lx[x]+ly[y]-g[x][y];
        if(temp==0)
        {
            visy[y]=1;
            if(linker[y]==-1 || DFS(linker[y]))
            {
                linker[y]=x;
                return 1;
            }
        }
        else if(slack[y]>temp)
            slack[y]=temp;
    }
    return 0;
}
int KM()
{
    memset(linker,-1,sizeof(linker));
    memset(ly,0,sizeof(ly));
    for(int i=1; i<=nx; ++i)
    {
        lx[i]=-INF;
        for(int j=1; j<=ny; ++j)
            if(g[i][j]>lx[i])
            lx[i]=g[i][j];
    }
    for(int x=1; x<=nx; ++x)
    {
        memset(slack,INF,sizeof(slack));
        while(1)
        {
            memset(visx,0,sizeof(visx));
            memset(visy,0,sizeof(visy));
            if(DFS(x))break;
            int d=INF;
            for(int i=1; i<=ny; ++i)
                if(!visy[i] && d>slack[i])
                d=slack[i];
            for(int i=1; i<=nx; ++i)
                if(visx[i])
                lx[i]-=d;
            for(int i=1; i<=ny; ++i)
            {
                if(visy[i])ly[i]+=d;
                else slack[i]-=d;
            }
        }
    }
    int ans=0;
    for(int i=1; i<=ny; ++i)
    {
        if(linker[i]!=-1)
            ans+=g[linker[i]][i];
    }
    return ans;
}
int main()
{
    int n;
    while(scanf("%d",&n)!=EOF)
    {
        for(int i=1; i<=n; ++i)
            for(int j=1; j<=n; ++j)
            scanf("%d",&g[i][j]);
        nx=ny=n;
        printf("%d\n",KM());
    }
    return 0;
}