POJ 1325 Machine Schedule【最小點覆蓋】

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E - Machine ScheduleTime Limit:1000MS     Memory Limit:10000KB     64bit IO Format:%I64d & %I64uSubmit Status Practice POJ 1325Appoint description: System Crawler  (2014-08-10)

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 5 100 1 11 1 22 1 33 1 44 2 15 2 26 2 37 2 48 3 39 4 30

Sample Output

3
之所以把題目粘下來是因為自己讀題不仔細wa一次
大意：
有兩台機器分別有n，m種模式，開始的時候全都在0模式
告訴你有一些任務可以在第一台機器的x1模式下完成也可以在第二台機器的x2模式下完成
並且每台機器切換模式需要重啟
問最少重啟多少次

分析：
左右集合分別為兩台機器的模式
邊為task
那麼只要選取最少的點覆蓋所有的邊即可
注意一點是一開始在0模式
所以只要對於0不建邊即可
網路流亦可以做

代碼：

#include <iostream>#include <cstdio>#include <cstring>#include <vector>using namespace std;const int maxn = 105;int n;vector<int> G[maxn];int vis[maxn];int Link[maxn];bool Find(int u) {    for(int i = 0; i < G[u].size(); i++) {        int v = G[u][i];        if(!vis[v]) {            vis[v] = 1;            if(Link[v] == -1 || Find(Link[v])) {                Link[v] = u;                return true;            }        }    }    return false;}int solve() {    int cnt = 0;    memset(Link, -1, sizeof(Link));    for(int i = 0; i < n; i++) {        memset(vis, 0, sizeof(vis));        if(Find(i)) cnt++;    }    return cnt;}int main() {    int m, k;    int a, b, c;    while(scanf("%d",&n) && n) {        scanf("%d %d",&m, &k);        n = max(n, m);        for(int i = 0; i < n; i ++) G[i].clear();        for(int i = 0; i < k; i++) {            scanf("%d %d %d",&a, &b, &c);            if(b == 0 || c == 0) continue;            G[b].push_back(c);        }        printf("%d\n",solve());    }    return 0;}

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