hdu 2255 奔小康赚大钱 KM模板题目

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

O(n^4)模板

#include <cstdio>

#include <cstring>

#include <iostream>

#define maxn 301

using namespace std;



const int inf = 99999999;

int w[maxn][maxn],link[maxn];

int lx[maxn],ly[maxn];

bool vtx[maxn],vty[maxn];

int nx,ny;



bool dfs(int i)

{

    int j;

    vtx[i] = true;

    for (j = 0; j < ny; ++j)

    {

        if (!vty[j] && lx[i] + ly[j] == w[i][j])

        {

            vty[j] = true;

            if (link[j] == -1 || dfs(link[j]))

            {

                link[j] = i;

                return true;

            }

        }

    }

    return false;

}

int KM()

{

    int i,j,k;

    for (i = 0; i < nx; ++i)

    {

        for (j = 0,lx[i] = -inf; j < ny; ++j)

        {

            lx[i] = max(lx[i],w[i][j]);

        }

    }

    for (i = 0; i < maxn; ++i)

    {

        link[i] = -1; ly[i] = 0;

    }

    for (i = 0; i < nx; ++i)

    {

        while (1)

        {

            for (j = 0; j < maxn; ++j) vtx[j] = vty[j] = false;

            if (dfs(i)) break;

            int d = inf;

            for (j = 0; j < nx; ++j)

            {

                if (vtx[j])

                {

                    for (k = 0; k < ny; ++k)

                    {

                        if (!vty[k]) d = min(d,lx[j] + ly[k] - w[j][k]);

                    }

                }

            }

            if (d == inf) return -1;

            for (j = 0; j < nx; ++j) if (vtx[j]) lx[j] -= d;

            for (j = 0; j < ny; ++j) if (vty[j]) ly[j] += d;

        }

    }

    int sum = 0;

    for (i = 0; i < ny; ++i)

    if (link[i] > -1) sum += w[link[i]][i];

    return sum;

}

int main()

{

    int i,j;

    while (~scanf("%d",&nx))

    {

        ny = nx;

        memset(w,0,sizeof(w));

        for (i = 0; i < nx; ++i)

        {

            for (j = 0; j < ny; ++j)

            {

                scanf("%d",&w[i][j]);

            }

        }

        printf("%d\n",KM());

    }

    return 0;

}