poj 1655 Balancing Act (树形dfs)

http://poj.org/problem?id=1655

同poj3107，只要求输出一个数值最小的点。

刚开始的答案值修改的num[]记录的，罪过罪过。。。

code:

#include<cstdio>
#include<cstring>
#define Max(a, b) a>b?a:b
using namespace std ;
const int MAX = 20001 ;
int k, n, Min, anspoint, ansnum ;
int vis[MAX], head[MAX], num[MAX] ;
struct Edge{
int v, next ;
}edge[2*MAX] ;
void addedge(int a, int b){
edge[k].v = b ;
edge[k].next = head[a] ;
head[a] = k ++ ;
}
void dfs(int x){
int i, v, min = -1 ;
num[x] = 1 ;
vis[x] = 1 ;
for(i=head[x]; i; i=edge[i].next){
v = edge[i].v ;
if(vis[v]) continue ;
dfs(v) ;
num[x] += num[v] ;
min = Max(min, num[v]) ;
}
min = Max(min, n-num[x]) ;
if(min<Min){
anspoint = x ;
Min = min ;
ansnum = min ;
}else if(min==Min&&anspoint>x){
anspoint = x ;
ansnum = min ;
}
}
int main(){
int t, x, y ;
scanf("%d", &t) ;
while(t--){
scanf("%d", &n) ;
k = 1 ;
memset(head, 0, sizeof(head)) ;
for(int i=1; i<n; i++){
scanf("%d%d", &x, &y) ;
addedge(x, y) ;
addedge(y, x) ;
}
memset(vis, 0, sizeof(vis)) ;
memset(num, 0, sizeof(num)) ;
Min = MAX ;
dfs(1) ;
printf("%d %d\n", anspoint, ansnum) ;
}
return 0 ;
}