【KM算法】HDU2255-奔小康赚大钱

KM算法的裸体。O（n^4）的模板，实际上在增广路径的时候依然有冗余，可以用bfs优化到O(n^3)。

#include <iostream>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <cstdlib>
#include <algorithm>
using namespace std;
const int MAXN=400+5;
const int INF=0x7fffffff;
int n,m;
int w[MAXN][MAXN];
int x[MAXN],y[MAXN]; 
int visx[MAXN],visy[MAXN],slack[MAXN];
int lk[MAXN];

int dfs(int u)
{
    visx[u]=1;
    for (int i=1;i<=n;i++)
    {
        int wt=x[u]+y[i]-w[u][i];
        if (!visy[i] && wt==0)
        {
            visy[i]=1;
            if (lk[i]==-1 || dfs(lk[i]))
            {
                lk[i]=u;
                return 1;
            }
        }
        else if (slack[i]>wt) slack[i]=wt;
    }
    return 0;
}

int KM()
{
    memset(lk,-1,sizeof(lk));
    for (int i=1;i<=n;i++)
    {
        y[i]=0;
        x[i]=-INF;
        for (int j=1;j<=n;j++) x[i]=max(x[i],w[i][j]);
    }
    for (int i=1;i<=n;i++)
    {
        memset(visx,0,sizeof(visx));
        memset(visy,0,sizeof(visy));
        memset(slack,127,sizeof(slack)); 
        while (!dfs(i))
        {
            int delta=INF;
            for (int j=1;j<=n;j++)
                if (!visy[j] && slack[j]<delta) delta=slack[j];
            for (int j=1;j<=n;j++) 
            {
                if (visx[j]) 
                {
                    x[j]-=delta;
                    visx[j]=0;
                }
                if (visy[j]) 
                {
                    y[j]+=delta;
                    visy[j]=0;
                }
            }
        } 
    }
    int ret=0;
    for (int i=1;i<=n;i++) ret+=x[i]+y[i];
    return ret;
}

void init()
{
    memset(w,0,sizeof(w));
    for (int i=1;i<=n;i++)
    {
        for (int j=1;j<=n;j++) 
            scanf("%d",&w[i][j]);
    }
}

int main()
{
    while (~scanf("%d",&n))
    {
        init();
        printf("%d
",KM());
    }
    return 0;
}