# hdu 2426 Interesting Housing Problem (二分图最佳匹配，km算法)

Posted by 111qqz on Wednesday, June 1, 2016

## TOC

hdu 2426 题目链接

``````/* ***********************************************
Author :111qqz
Created Time :2016年06月01日 星期三 19时35分04秒
File Name :code/hdu/2426.cpp
************************************************ */

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <string>
#include <cmath>
#include <cstdlib>
#include <ctime>
#define fst first
#define sec second
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
#define ms(a,x) memset(a,x,sizeof(a))
typedef long long LL;
#define pi pair < int ,int >
#define MP make_pair

using namespace std;
const double eps = 1E-8;
const int dx4[4]={1,0,0,-1};
const int dy4[4]={0,-1,1,0};
const int inf = 0x3f3f3f3f;
const int N=505;
int n,m,e;
int w[N][N];
int lx[N],ly[N];
bool visx[N],visy[N];
int slk[N];

void init()
{
ms(w,0xc0);
}

bool find( int u)
{
visx[u] = true;

for ( int v = 1 ; v <= m ; v++)
{
if (visy[v]) continue;
int tmp = lx[u] + ly[v] - w[u][v];
if (tmp==0)
{
visy[v] = true;
{
return true;
}
}else if (tmp<slk[v]) slk[v] = tmp;
}
return false;
}
int KM()
{
ms(lx,0xc0);
ms(ly,0);

for ( int i = 1 ; i <= n ; i++)
for ( int j = 1 ; j <= m ; j++)
lx[i] = max(lx[i],w[i][j]);

for ( int i = 1 ; i <= n ; i++) if (lx[i]==-inf-1) return -1;

for ( int i = 1 ; i <= n ; i++)
{
ms(slk,0x3f);

while (true)
{
ms(visx,false);
ms(visy,false);

if (find(i)) break;

int d = inf;

for ( int j = 1 ; j <= m ; j++)
if (!visy[j]&&slk[j]<d) d = slk[j];
// cout<<"d:"<<d<<endl;

for ( int j = 1 ; j <= n ; j++)
if (visx[j]) lx[j]-=d;
for ( int j = 1 ;j  <= m ; j++)
if (visy[j]) ly[j]+=d; else slk[j]-=d;

}
}

int res = 0 ;
for ( int i = 1 ; i <= m ; i++)

//   if (res<-5E8) res = -1;
return res;
}
int main()
{
#ifndef  ONLINE_JUDGE
freopen("code/in.txt","r",stdin);
#endif
int cas = 0 ;
while (scanf("%d%d%d",&n,&m,&e)!=EOF)
{

init();
for ( int i = 1 ; i <= e ; i++)
{
int u,v,cost;
scanf("%d%d%d",&u,&v,&cost);
u++;
v++;
if (cost<0) continue;//? mdzz，读漏了。。喜欢程度为负是不能住的。
w[u][v] = cost;
}

printf("Case %d: ",++cas);
if (n>m)  //学生比房间数多。
{
puts("-1");
continue;
}

int ans = KM();
printf("%d\n",ans);
}

#ifndef ONLINE_JUDGE
fclose(stdin);
#endif
return 0;
}
``````

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