UVa-10763-Foreign Exchange
AOAPC I: Beginning Algorithm Contests (Rujia Liu) :: Volume 4. Algorithm Design
// 10763 - Foreign Exchange #include <iostream> #define MAXN 500000 using 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; }