HDU 1150 Machine Schedule

Machine Schedule

Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others)

Total Submission(s): 103 Accepted Submission(s): 68

Problem Description

As we all know, machine scheduling is a very classical problem in computer science and has been studied for a very long history. Scheduling problems differ widely in the nature of the constraints that must be satisfied and the type of schedule desired. Here we consider a 2-machine scheduling problem.

There are two machines A and B. Machine A has n kinds of working modes, which is called mode_0, mode_1, …, mode_n-1, likewise machine B has m kinds of working modes, mode_0, mode_1, … , mode_m-1. At the beginning they are both work at mode_0.

For k jobs given, each of them can be processed in either one of the two machines in particular mode. For example, job 0 can either be processed in machine A at mode_3 or in machine B at mode_4, job 1 can either be processed in machine A at mode_2 or in machine B at mode_4, and so on. Thus, for job i, the constraint can be represent as a triple (i, x, y), which means it can be processed either in machine A at mode_x, or in machine B at mode_y.

Obviously, to accomplish all the jobs, we need to change the machine's working mode from time to time, but unfortunately, the machine's working mode can only be changed by restarting it manually. By changing the sequence of the jobs and assigning each job to a suitable machine, please write a program to minimize the times of restarting machines. 

 

Input

The input file for this program consists of several configurations. The first line of one configuration contains three positive integers: n, m (n, m < 100) and k (k < 1000). The following k lines give the constrains of the k jobs, each line is a triple: i, x, y.

The input will be terminated by a line containing a single zero.

 

Output

The output should be one integer per line, which means the minimal times of restarting machine.

 

Sample Input

5 5 10
0 1 1
1 1 2
2 1 3
3 1 4
4 2 1
5 2 2
6 2 3
7 2 4
8 3 3
9 4 3
0

 

Sample Output

3

 

Source

Asia 2002, Beijing (Mainland China)

 

Recommend

Ignatius.L

题目给出了 k项任务 ， 然后有A ， B两种机器 （机器A有n中模式,机器B 有m种模式），  任务 ki  可以在 Ax 或 By模式下完成 ， 

然后机器在模式转换的时候需要重启， 然后要求最少的重启次数去完成所有的任务。

这个确实想了挺久，用最大二分匹配解决最少点覆盖问题 ， 就是用尽量少的点来覆盖（与边相关联）所有的边 。

然后这题要把任务看成边去构图，求一次最大匹配就行了。

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;
const int N = 111;
int n , m , k;
int g[N][N] , lx[N];
bool vis[N];

bool dfs(int u )
{
    for(int v = 1; v < m ; ++v ){

        if( g[u][v] && !vis[v] ){
            vis[v] = 1 ;
            if( lx[v] == -1 ||dfs (lx[v]) ){
                lx[v] = u ;
                return true ;
            }
        }
    }
    return false ;
}


int KM()
{
    int res = 0;
    memset(lx , -1 ,sizeof lx );
    for(int i = 1 ; i < n ; ++i ){
        memset (vis , false , sizeof vis );
        if( dfs(i) ) res++;
    }
    return res ;
}
int main()
{
    #ifdef LOCAL
        freopen("in.txt","r",stdin);
    #endif

    int a , x , y ;

    while(cin>>n){

        if(!n)break;
        cin>>m>>k;
        memset(g , 0 ,sizeof  g) ;

        while(k-- )
        {
            cin>>a >> x >> y ;
            if(x == 0 || y == 0 ) continue;
            g[x][y] = 1 ;
        }
        printf("%d
",KM());
    }
    return 0 ;
}