UVa-10763-Foreign Exchange

AOAPC I: Beginning Algorithm Contests (Rujia Liu) :: Volume 4. Algorithm Design

// 10763 - Foreign Exchange#include <iostream>#define MAXN 500000using namespace std;int a[MAXN+1];int main(void){int i, n, x, y;while(cin >> n && n != 0){for(i = 1; i <= MAXN; i++)a[i] = i;for(i = 1; i <= n; i++){cin >> x >> y;swap(a[x], a[y]);}for(i = 1; i <= MAXN; i++)if(a[i] != i){cout << "NO" << endl;break;}if(i == MAXN+1)cout << "YES" << endl;}return 0;}