POJ 3107 Godfather (树重心)
题目链接：http://poj.org/problem?id=3107
题意:
数重心，并按从小到大输出。
思路:
dfs
1 #include <iostream> 2 #include <cstdio> 3 #include <cstring> 4 #include <vector> 5 using namespace std; 6 const int N = 5e4 + 5; 7 struct Edge { 8 int next, to; 9 }edge[N << 1]; 10 vector <int> G[N]; 11 int dp[N], n, head[N], cnt; 12 13 inline void add(int u, int v) { 14 edge[cnt].next = head[u]; 15 edge[cnt].to = v; 16 head[u] = cnt++; 17 } 18 19 int dfs(int u, int p) { 20 dp[u] = 0; 21 int sum = 0; 22 for(int i = head[u]; ~i; i = edge[i].next) { 23 int v = edge[i].to; 24 if(v == p) 25 continue; 26 int temp = dfs(v, u); 27 dp[u] = max(dp[u], temp); 28 sum += temp; 29 } 30 dp[u] = max(dp[u], n - sum - 1); 31 return sum + 1; 32 } 33 34 int main() 35 { 36 while(~scanf("%d", &n)) { 37 for(int i = 1; i <= n; ++i) { 38 head[i] = -1; 39 } 40 cnt = 0; 41 for(int i = 1; i < n; ++i) { 42 int u, v; 43 scanf("%d %d", &u, &v); 44 add(u, v); 45 add(v, u); 46 } 47 dfs(1, -1); 48 int Max = n; 49 vector <int> ans; 50 for(int i = 1; i <= n; ++i) { 51 Max = min(Max, dp[i]); 52 } 53 for(int i = 1; i <= n; ++i) { 54 if(Max == dp[i]) { 55 ans.push_back(i); 56 } 57 } 58 for(int i = 0; i < ans.size(); ++i) { 59 if(i == ans.size() - 1) { 60 printf("%d\n", ans[i]); 61 } else { 62 printf("%d ", ans[i]); 63 } 64 } 65 } 66 return 0; 67 }
