POJ 3107 - Godfather

// poj3107 Godfather
#include <cstdio>
#include <cstring>
#define NDEBUG


#define MAXN    50005

using namespace std;

int N;
int edgefw[MAXN*2], edge[MAXN*2], head[MAXN], eptr;

#define EI(j, k)    ({ \
    edge[eptr] = k, edgefw[eptr] = head[j];        head[j] = eptr++;    })

int dp[MAXN], dp2[MAXN];
char vis[MAXN];

void dfs(int i)
{
    vis[i] = 1;
    int p, maxk = 0, sumn = 1;
    for(p = head[i]; p>=0; p = edgefw[p]) {
        int t = edge[p];
        if (!vis[t]) {
            if (!dp2[t]) dfs(t);
            sumn += dp2[t];
            if (maxk < dp2[t])
                    maxk = dp2[t];
        }
    }
    if (sumn != N && N - sumn > maxk) maxk = N - sumn;
    dp[i] = maxk, dp2[i] = sumn;
}

int main(void)
{
    #ifndef NDEBUG
    freopen("poj3107.in", "r", stdin);
    #endif // NDEBUG
    scanf("%d", &N);
    memset(head, -1, sizeof(int) * N), eptr = 0;
    int i, j, root;
    root = 0;
    for(i=1; i<N; ++i) {
        int k;
        scanf("%d%d", &j, &k);
        --j,--k; EI(j, k), EI(k, j);
        if (root == k) root = j;
    }
    dfs(root);
    j = 0;
    for(i = 1; i < N; ++i)
        if (dp[i] < dp[j])
            j = i;
    root = 0;
    for(i = 0; i < N; ++i)
        if (dp[i] == dp[j]) {
            printf("%d", ++i);
            break;
        }
    for(; i<N; ++i)
        if (dp[i] == dp[j])
            printf(" %d", i+1);
    putchar(‘\n‘);
    return 0;
}