Submission #7261333

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef pair<ll,ll> pll;
typedef vector<bool> vb;
const ll oo = 0x3f3f3f3f3f3f3f3f;
const double eps = 1e-9;
#define sz(c) ll((c).size())
#define all(c) begin(c), end(c)
#define FOR(i,a,b) for (ll i = (a); i < (b); i++)
#define FORD(i,a,b) for (ll i = (b)-1; i >= (a); i--)
#define mp make_pair
#define pb push_back
#define eb emplace_back
#define xx first
#define yy second
#define TR(X) ({ if(1) cerr << "TR: " << (#X) << " = " << (X) << endl; })

int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	
	ll n; cin >> n;
	vvl order(n,vl(n-1));
	FOR(i,0,n) FOR(j,0,n-1) {
		ll x; cin >> x;
		order[i][j] = x-1;
	}
	vl ptr(n);
	
	ll res = 0;
	while (true) {
		bool change = false;
		vb mark(n);
		FOR(i,0,n) if (ptr[i] < n-1 && !mark[i]) {
			ll j = order[i][ptr[i]];
			if (ptr[j] < n-1 && !mark[j] && order[j][ptr[j]] == i) {
				ptr[i]++, ptr[j]++;
				mark[i] = mark[j] = true;
				change = true;
			}
		}
		if (!change) break;
		res++;
	}
	
	if (ptr != vl(n,n-1)) res = -1;
	cout << res << endl;
}

Submission Info

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