#include <bits/stdc++.h>

#define MODE 1

#if MODE == 0
#define debug(x) cout << #x << ": " << x << endl
#define log(x) cout << x << endl
#define test(x) x
#else
#define debug(x)
#define log(x)
#define test(x)
#endif

#define M 1000000007
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
#define fi first
#define se second

using namespace std;
using ll = long long;
using ld = long double;
using uint = unsigned int;
using ull = unsigned long long;
using pii = pair<int, int>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;

void dfs(int u, int p, int i, vector<vector<pii>> &adj, vector<array<bool, 2>> &dp, vector<int> &cnt) {
    for (auto v: adj[u]) if (v.fi != p) {
        dfs(v.fi, u, v.se, adj, dp, cnt);
    }
    
    if (p == -1)
        return;
    
    dp[i][u>p] = !cnt[u];
    cnt[p] += dp[i][u>p];
}


void dfs2(int u, int p, int i, vector<vector<pii>> &adj, vector<array<bool, 2>> &dp, vector<int> &cnt) {
    for (auto v: adj[u]) if (v.fi != p) {
        if (cnt[u] == 0)
            dp[v.se][u>v.fi] = 1;
        else if (cnt[u] >= 2)
            dp[v.se][u>v.fi] = 0;
        else if (dp[v.se][v.fi>u])
            dp[v.se][u>v.fi] = 1;
        else
            dp[v.se][u>v.fi] = 0;
        
        cnt[v.fi] += dp[v.se][u>v.fi];
        dfs2(v.fi, u, v.se, adj, dp, cnt);
    }
}

void solve() {
    int n;
    cin >> n;
    
    vector<vector<pii>> adj(n);
    for (int i = 0; i < n-1; ++i) {
        int a, b;
        cin >> a >> b;
        --a;--b;
        adj[a].push_back({b, i});
        adj[b].push_back({a, i});
    }
    
    vector<array<bool, 2>> dp(n-1, {0, 0});
    vector<int> cnt(n, 0);
    
    dfs(0, -1, -1, adj, dp, cnt);
    dfs2(0, -1, -1, adj, dp, cnt);
    
    for (int i = 0; i < n; ++i) {
        if (cnt[i] == 0) {
            cout << "Alice\n";
            return;
        }
    }
    
    cout << "Bob\n";
}

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(nullptr);

    solve();

    return 0;
}

#include <bits/stdc++.h>

#define MODE 0

#if MODE == 0
#define debug(x) cout << #x << ": " << x << endl
#define log(x) cout << x << endl
#define test(x) x
#else
#define debug(x)
#define log(x)
#define test(x)
#endif

#define M 1000000007
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
#define fi first
#define se second

using namespace std;
using ll = long long;
using ld = long double;
using uint = unsigned int;
using ull = unsigned long long;
using pii = pair<int, int>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;

void dfs(int u, int p, vector<vector<int>> &adj, vector<array<bool, 2>> &bad) {
    int cnt[2] = {0, 0};
    int tot = 0;
    for (int v: adj[u]) if (v != p) {
        dfs(v, u, adj, bad);
        cnt[0] += bad[v][0];
        cnt[1] += bad[v][1];
        ++tot;
    }
    
    bad[u][0] = cnt[1];
    bad[u][1] = !(cnt[1] == 1 && cnt[0] == tot - 1);
}

void solve() {
    int n;
    cin >> n;
    
    vector<vector<int>> adj(n);
    for (int i = 0; i < n-1; ++i) {
        int a, b;
        cin >> a >> b;
        --a;--b;
        adj[a].push_back(b);
        adj[b].push_back(a);
    }
    
    vector<array<bool, 2>> bad(n, {0, 0});
    dfs(0, -1, adj, bad);
    
    cout << (bad[0][1] ? "Alice" : "Bob") << '\n';
}

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(nullptr);

    solve();

    return 0;
}

#include <bits/stdc++.h>

#define MODE 0

#if MODE == 0
#define debug(x) cout << #x << ": " << x << endl
#define log(x) cout << x << endl
#define test(x) x
#else
#define debug(x)
#define log(x)
#define test(x)
#endif

#define M 1000000007
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
#define fi first
#define se second

using namespace std;
using ll = long long;
using ld = long double;
using uint = unsigned int;
using ull = unsigned long long;
using pii = pair<int, int>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;

void dfs(int u, int p, vector<vector<int>> &adj, vector<int> &dp) {
    int sum = 0;
    for (int v: adj[u]) if (v != p) {
        dfs(v, u, adj, dp);
        sum += dp[v];
    }
    
    dp[u] = (sum == 0 ? 1 : sum - 1);
}

void solve() {
    int n;
    cin >> n;
    
    vector<vector<int>> adj(n);
    for (int i = 0; i < n-1; ++i) {
        int a, b;
        cin >> a >> b;
        --a;--b;
        adj[a].push_back(b);
        adj[b].push_back(a);
    }
    
    vector<int> dp(n, 0);
    dfs(0, -1, adj, dp);
    
    cout << (dp[0] ? "Alice" : "Bob") << '\n';
}

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(nullptr);

    solve();

    return 0;
}

Input:
6
1 2
2 3
3 4
3 5
3 6

Editorial solution output:
Bob

Correct output:
Alice