树形DP，还是求最大独立集，加上判断唯一性，这题我就卡在唯一性上了。
1 #include <stdio.h> 2 #include <string.h> 3 #define N 205 4 int fst[N],nxt[N],v[N],n,m; 5 int only[N][2],dp[N][2]; 6 char name[N][105]; 7 int max(int a, int b) 8 { 9 return a>b ?a :b; 10 } 11 int find(char *t) 12 { 13 for(int i = 0; i < m; i++) 14 if(!strcmp(name[i],t)) 15 return i; 16 return -1; 17 } 18 void dfs(int u) 19 { 20 int e,i; 21 dp[u][0] = 0; 22 dp[u][1] = 1; 23 only[u][0] = only[u][1] = 1; 24 for(i = fst[u]; i != -1; i = nxt[i]) 25 { 26 e = v[i]; 27 dfs(e); 28 dp[u][0] += max(dp[e][0],dp[e][1]); 29 if(dp[e][0]==dp[e][1]) only[u][0] = 0; 30 else if((dp[e][0] > dp[e][1]) && only[u][0]) 31 only[u][0] = only[e][0]; 32 else if(only[u][0]) 33 only[u][0] = only[e][1]; 34 dp[u][1] += dp[e][0]; 35 if(only[u][1]) only[u][1] = only[e][0]; 36 } 37 //printf("dp[%d][0]: %d\ndp[%d][1]: %d\n",u,dp[u][0],u,dp[u][1]); 38 } 39 int main() 40 { 41 int i,u; 42 char s[105],t[105]; 43 while(scanf("%d",&n),n) 44 { 45 memset(fst,-1,sizeof fst); 46 scanf("%s",name[0]); 47 for(i = m = 1; i < n; i++) 48 { 49 scanf("%s %s",s,t); 50 u = find(t); 51 v[i] = find(s); 52 if(u == -1) 53 u = m, strcpy(name[m++],t); 54 if(v[i] == -1) 55 v[i] = m, strcpy(name[m++],s); 56 nxt[i] = fst[u]; 57 fst[u] = i; 58 } 59 dfs(0); 60 if(dp[0][0] > dp[0][1]) 61 { 62 printf("%d ",dp[0][0]); 63 printf(only[0][0] ?"Yes\n" :"No\n"); 64 } 65 else if(dp[0][0] < dp[0][1]) 66 { 67 printf("%d ",dp[0][1]); 68 printf(only[0][1] ?"Yes\n" :"No\n"); 69 } 70 else 71 printf("%d No\n",dp[0][1]); 72 } 73 return 0; 74 }