poj 1129 -- Channel Allocation

 1 /*======================================================================
 2  *           Author :   kevin
 3  *         Filename :   ChannelAllocation.cpp
 4  *       Creat time :   2014-08-07 09:11
 5  *      Description :
 6 ========================================================================*/
 7 #include <iostream>
 8 #include <algorithm>
 9 #include <cstdio>
10 #include <cstring>
11 #include <queue>
12 #include <cmath>
13 #define clr(a,b) memset(a,b,sizeof(a))
14 #define M 30
15 using namespace std;
16 int grap[M][M],color[M];
17 int n,ans;
18 void DFS(int num)
19 {
20     if(num == n){
21         return ;
22     }
23     for(int i = 1; i <= n; i++){
24         int flag = 0;
25         for(int j = 0; j <= num; j++){
26             if(grap[num][j] && color[j] == i){
27                 flag = 1;
28                 break;
29             }
30         }
31         if(!flag){
32             color[num] = i;
33             if(ans < i){
34                 ans = i;
35             }
36             DFS(num+1);
37             break;
38         }
39     }
40 }
41 int main(int argc,char *argv[])
42 {
43     while(scanf("%d",&n)!=EOF && n){
44         getchar();
45         clr(grap,0);
46         clr(color,0);
47         char str[100];
48         for(int i = 0; i < n; i++){
49             gets(str);
50             int a = str[0] - ‘A‘;
51             int len = strlen(str);
52             for(int i = 2; i < len; i++){
53                 grap[a][str[i] - ‘A‘] = 1;
54             }
55         }
56         ans = 0;
57         DFS(0);
58         if(ans == 1){
59             printf("1 channel needed.\n");
60         }
61         else printf("%d channels needed.\n",ans);
62     }
63     return 0;
64 }