看了chenxing老湿的代码，我真心为自己智商捉鸡啊。。一遍dfs搞定啊。。
1 #include <cstdio> 2 #include <cstring> 3 #define maxn 110 4 int first[maxn],v[maxn*2],next[maxn*2]; 5 int len,e; 6 inline int max(int a,int b){ 7 return a > b ? a : b; 8 } 9 10 void init(){ 11 e = 0; 12 memset(first,-1,sizeof(first)); 13 } 14 15 void add_edge(int a,int b){ 16 v[e] = b; 17 next[e] = first[a]; 18 first[a] = e++; 19 } 20 21 int dfs(int u,int fa){ 22 int ret = 0,maxdep; 23 for(int i = first[u];i != -1;i = next[i]){ 24 if(v[i] == fa) continue; 25 maxdep = dfs(v[i],u); 26 len = max(len,ret + maxdep + 1); 27 ret = max(ret,maxdep + 1); 28 } 29 return ret; 30 } 31 32 int main(){ 33 freopen("input.txt", "r", stdin); 34 freopen("output.txt", "w", stdout); 35 int n,m; 36 while(scanf("%d",&n) != EOF){ 37 int ans = 0; 38 while(n--){ 39 scanf("%d",&m); 40 init(); 41 len = 0; 42 for(int i = 0;i < m-1;i++){ 43 int a,b; 44 scanf("%d%d",&a,&b); 45 add_edge(a,b); 46 add_edge(b,a); 47 } 48 dfs(1,-1); 49 ans += len; 50 } 51 printf("%d ",ans); 52 } 53 }