POJ 1655 Balancing Art

Posted on Edited on In 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
const int N = 20001, M = 2 * N;
int t, n, u, v, h[N], e[M], ne[M], idx;
bool visited[N];
int ans, node;
void add(int u, int v) {
    e[idx] = v, ne[idx] = h[u], h[u] = idx++;
}
int dfs(int u) { // return size of the tree `u`.
    visited[u] = true;
    int res = 0, // max size of connected componet.
       sum = 1; // size of current tree (whose root node is `u`).
    for (int i = h[u]; ~i; i = ne[i]) {
        int v = e[i];
        if (visited[v]) continue;
        int s = dfs(v);
        res = max(res, s);
        sum += s;
    }
    res = max(res, n - sum);
    if (res < ans) {
        ans = res;
        node = u;
    }
    return sum;
}
int main() {
    scanf("%d", &t);
    while (t--) {
        scanf("%d", &n);
        idx = 0, ans = n;
        memset(h, -1, (n + 1) * 4);
        memset(visited, false, n + 1);
        for (int i = 1; i < n; ++i) {
            scanf("%d%d", &u, &v);
            add(u, v), add(v, u);
        }
        dfs(1);
        printf("%d %d\n", node, ans);
    }
    return 0;
}