RT，WA10，https://codeforces.com/gym/103698/problem/D

#include <bits/stdc++.h>
using namespace std;
char c; 
struct no {int x, y;};
queue < no > que;
vector < int > P, Q;
map < int, int > V1, V2;
inline void OP () {for (int i = 0;i < P.size (); ++ i) cout << P[i] << ' '; cout << endl;}
inline void OQ () {for (int i = 0;i < Q.size (); ++ i) cout << Q[i] << ' '; cout << endl;}
inline void solve () {
	while (!que.empty ()) {
		no frt = que.front (); que.pop ();
		int ans = 2;
		if (frt.x == frt.y) {
			cout << "-1\n"; exit (0);
		} 
		int ans1, ans2; ans1 = ans2 = 1;
		if (V1[frt.y] == 1 || V2[frt.x] == 1) {
			ans1 = 0;
		}
		if (V1[frt.x] == 1 || V2[frt.y] == 1) {
			ans2 = 0;
		}
		if (ans1 + ans2 == 0) {
			cout << "-1\n"; exit (0);
		}
		if (V1[frt.y] == 1 || V2[frt.x] == 1) {
			swap (frt.x, frt.y);
		}
		if (V1[frt.x] == 0) P.push_back (frt.x);
		if (V2[frt.y] == 0) Q.push_back (frt.y);
		V1[frt.x] = 1;
		V2[frt.y] = 1;
	}
	cout << min (P.size (), Q.size ()) << endl;
	sort (P.begin (), P.end ());
	sort (Q.begin (), Q.end ());
	if (P.size () != Q.size ()) {
		if (P.size () < Q.size ()) OP ();
		else OQ ();
	}
	else {
		if (P[0] < Q[0]) OP ();
		else OQ ();
	}
}
int n;
signed main () {
	cin >> n;
	for (int i = 1;i <= n; ++ i) {
		for (int j = 1;j <= n; ++ j) {
			cin >> c;
			if (c == '1') {
				que.push ({min (i, j), max (i, j)}); 
//				cout << min (i, j) << ' ' << max (i, j) << endl;
			}
		}
	}
	if (que.empty ()) cout << "0\n";
	else solve ();
}