CodeForces 490

//题目的意思是每一个人报出他前后两人的编码，要求还原队列

#include<cstdio>typedef long long LL;#define N 1000010int a[N]={0}, b[N]={0}, ans[N]={0};bool v[N]={0};int main() {int n,ba,fr,k,i,tmp;scanf("%d", &n);for ( i = 1; i <= n; i++) {scanf("%d%d", &fr, &ba);a[fr] = ba; b[ba] = fr;v[fr] = v[ba] = 1;}for (tmp = a[0],k=2; tmp; tmp = a[tmp], k += 2) {//偶数位ans[k] = tmp; v[tmp] = 0;}i=1;while(!v[i]) i++;while (b[i]) i = b[i];//寻找起点//for ( k=1; tmp; tmp = a[tmp], k += 2) ans[k] = tmp;for (i = 1; i <= n; i++)printf("%d%s", ans[i], i == n ? "\n" : " ");return 0;}

蛮好的处理方式。。。。