Channel Allocation 贪心涂色

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <cmath>
 5 #include <algorithm>
 6 #include <string>
 7 #include <vector>
 8 #include <set>
 9 #include <map>
10 #include <stack>
11 #include <queue>
12 #include <sstream>
13 #include <iomanip>
14 using namespace std;
15 typedef long long LL;
16 const int INF = 0x4fffffff;
17 const double EXP = 1e-5;
18 const int MS = 28;
19 const int SIZE = 100005;
20 
21 
22 int edges[MS][MS];
23 char str[MS];
24 int used[MS];
25 int color[MS];
26 int ans,n;
27 
28 void greedy()
29 {
30       for(int i=0;i<n;i++)
31       {
32             memset(used,0,sizeof(used));
33             for(int j=0;j<n;j++)
34             {
35                   if(edges[i][j]&&color[j]!=-1)
36                         used[color[j]]=1;
37             }
38             int k;
39             for(k=0;k<i;k++)
40             {
41                   if(!used[k])
42                         break;
43             }
44             color[i]=k;
45       }
46       ans=0;
47       for(int i=0;i<n;i++)
48             if(ans<color[i])
49                   ans=color[i];
50       ans++;
51 }
52 
53 
54 int main()
55 {
56       while(scanf("%d",&n)&&n)
57       {
58             memset(color,0xff,sizeof(color));
59             memset(edges,0,sizeof(edges));
60             for(int i=0;i<n;i++)
61             {
62                   scanf("%s",str);
63                   int len=strlen(str);
64                   for(int j=2;j<len;j++)
65                         edges[i][str[j]-‘A‘]=edges[str[j]-‘A‘][i]=1;
66             }
67             greedy();
68             if(ans==1)                    //   注意单复数
69                   printf("%d channel needed.\n",ans);
70             else
71                   printf("%d channels needed.\n",ans);
72       }
73       return 0;
74 }