Submission #1243109

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Source Code Expand

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

#define pb push_back
#define mp make_pair
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef complex<double> point;
#define xx real()
#define yy imag()

#define REP(i, a, b) for(int i = (a); i < (int)(b); i++)
#define REPN(i, a, b) for(int i = (a); i <= (int)(b); i++)
#define FA(it, x) for(__typeof((x).begin()) it = (x).begin(); it != (x).end(); it++)
#define SZ(x) (int)(x).size()
#define BE(x) (x).begin(), (x).end()
#define SORT(x) sort(BE(x))
#define _1 first
#define _2 second

#define x1 gray_cat_x1
#define y1 gray_cat_y1

template<class T> T gcd(T a, T b) { return b ? gcd(b, a % b) : a; }

#define file "cycle"

const double EPS = 1e-9;
const double PI = acos(-1.);
const int INF = 1e9;
const ll MOD = 1e9 + 7;

const int MAXN = 2e5 + 5;

vi g1[MAXN], g2[MAXN];

int used1[MAXN], used2[MAXN];

int dis1[MAXN], dis2[MAXN];

int tin2[MAXN], tout2[MAXN], _t, prv2[MAXN];

bool is_prv(int a, int b){
	return tin2[a] <= tin2[b] && tout2[b] <= tout2[a];
}

bool check_dis_le_2(int a, int b){
	if (abs(dis2[a] - dis2[b]) > 2){
		return false;
	}
	if (is_prv(a, b) || is_prv(b, a)){
		return true;
	}
	if (prv2[a] == prv2[b]){
		return true;
	}
	return false;
}

int ans;
int ans1;

void dfs1(int s){
	used1[s] = 1;
	ans = max(ans, 2 * dis2[s]);
	REP(i, 0, SZ(g1[s])){
		int to = g1[s][i];
		if (!used1[to]){
			dis1[to] = dis1[s] + 1;
			if (!check_dis_le_2(s, to)){
				ans1 = 1;
			}
			if (dis1[to] < dis2[to]){
				dfs1(to);
			}
		}
	}
}

void dfs2(int s){
	used2[s] = 1;
	tin2[s] = tout2[s] = _t++;
	REP(i, 0, SZ(g2[s])){
		int to = g2[s][i];
		if (!used2[to]){
			prv2[to] = s;
			dis2[to] = dis2[s] + 1;
			dfs2(to);
			tout2[s] = tout2[to];
		}
	}
}

void solve(){
	int n, a, b, s1, s2;
	scanf("%d%d%d", &n, &s1, &s2);
	REP(i, 1, n){
		scanf("%d%d", &a, &b);
		g1[a].pb(b);
		g1[b].pb(a);
	}
	REP(i, 1, n){
		scanf("%d%d", &a, &b);
		g2[a].pb(b);
		g2[b].pb(a);
	}
	dfs2(s2);
	dfs1(s1);
	if (ans1 == 1){
		ans = -1;
	}
	printf("%d\n", ans);
}	

int main(){

	//freopen(file".in", "r", stdin); freopen(file".out", "w", stdout);
	int t = 1;
	//cin >> t;
	while(t--){
		solve();	
	}
}

Submission Info

Compile Error

./Main.cpp: In function ‘void solve()’:
./Main.cpp:97:31: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d%d", &n, &s1, &s2);
                               ^
./Main.cpp:99:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d", &a, &b);
                        ^
./Main.cpp:104:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d", &a, &b);
                        ^

Judge Result