poj 3342 树形dp

还是简单的树形dp，不过要判断最优解是否有多种。

  1 #include <iostream>
  2 #include <cstring>
  3 #include <cstdio>
  4 #include <map>
  5 using namespace std;
  6 
  7 const int N = 201;
  8 int head[N];
  9 int dp[N][2];
 10 bool flag[N][2];
 11 int n, e, cnt;
 12 map<string, int> mp;
 13 
 14 struct Edge
 15 {
 16     int v, next;
 17 } edge[N];
 18 
 19 void addEdge( int u, int v )
 20 {
 21     edge[e].v = v;
 22     edge[e].next = head[u];
 23     head[u] = e++;
 24 }
 25 
 26 void dfs( int u )
 27 {
 28     dp[u][0] = 0, dp[u][1] = 1;
 29     for ( int i = head[u]; i != -1; i = edge[i].next )
 30     {
 31         int v = edge[i].v;
 32         dfs(v);
 33         dp[u][1] += dp[v][0];
 34         if ( flag[v][0] )
 35         {
 36             flag[u][1] = true;
 37         }
 38         if ( dp[v][0] > dp[v][1] )
 39         {
 40             dp[u][0] += dp[v][0];
 41             if ( flag[v][0] )
 42             {
 43                 flag[u][0] = true;
 44             }
 45         }
 46         else if ( dp[v][0] < dp[v][1] )
 47         {
 48             dp[u][0] += dp[v][1];
 49             if ( flag[v][1] )
 50             {
 51                 flag[u][0] = true;
 52             }
 53         }
 54         else
 55         {
 56             dp[u][0] += dp[v][0];
 57             flag[u][0] = true;
 58         }
 59     }
 60 }
 61 
 62 char str1[N], str2[N];
 63 
 64 int main ()
 65 {
 66     while ( scanf("%d", &n), n )
 67     {
 68         e = 0;
 69         cnt = 1;
 70         memset( head, -1, sizeof(head) );
 71         mp.clear();
 72         scanf("%s", str1);
 73         mp[str1] = cnt++;
 74         for ( int i = 1; i < n; i++ )
 75         {
 76             scanf("%s%s", str1, str2);
 77             if ( mp.count(str1) == 0 )
 78             {
 79                 mp[str1] = cnt++;
 80             }
 81             if ( mp.count(str2) == 0 )
 82             {
 83                 mp[str2] = cnt++;
 84             }
 85             addEdge( mp[str2], mp[str1] );
 86         }
 87         memset( flag, false, sizeof(flag) );
 88         dfs(1);
 89         if ( dp[1][0] > dp[1][1] )
 90         {
 91             printf("%d", dp[1][0]);
 92             if ( !flag[1][0] )
 93                 printf(" Yes\n");
 94             else
 95                 printf(" No\n");
 96         }
 97         else if ( dp[1][1] > dp[1][0] )
 98         {
 99             printf("%d", dp[1][1]);
100             if ( !flag[1][1] )
101                 printf(" Yes\n");
102             else
103                 printf(" No\n");
104         }
105         else
106         {
107             printf("%d No\n", dp[1][0]);
108         }
109     }
110     return 0;
111 }

 

posted @ 2015-07-20 10:51  hxy_has_been_used  阅读(213)  评论(0)  编辑  收藏  举报