Codeforces 490B Queue(水)

题目链接：Codeforces 490B Queue

#include <cstdio>#include <cstring>#include <algorithm>using namespace std;const int maxn = 1e6 + 5;const int maxm = 1e5 * 2 + 5;int N, ans[maxm];int v[maxn], f[maxn];void init () {scanf("%d", &N);memset(v, 0, sizeof(v));memset(f, -1, sizeof(f));int a, b;for (int i = 0; i < N; i++) {scanf("%d%d", &a, &b);f[a] = b;v[a]++, v[b]++;}}void solve(int b, int x) {while (b > 0) {ans[x] = b;x += 2;b = f[b];}}int main () {init();solve(f[0], 2);for (int i = 1; i <= 1e6; i++)if (v[i] == 1 && f[i] >= 0) {solve(i, 1);break;}for (int i = 1; i <= N; i++)printf("%d%c", ans[i], i == N ? '\n' : ' ');return 0;}