Problem p02850 (C++)

Buggy submission (status: Runtime Error):
#include <algorithm>
#include <bitset>
#include <cfloat>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <deque>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <limits.h>
#include <list>
#include <map>
#include <math.h>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}

using namespace std;
#define int long long
#define ll long long
#define rep(i, n) for (ll i = 0; i < (n); i++)
#define FOR(i, a, b) for (ll i = (a); i < (b); i++)
#define FORR(i, a, b) for (ll i = (a); i <= (b); i++)
#define repr(i, n) for (ll i = n; i >= 0; i--)
#define P pair<ll, ll>
#define sz(x) (ll) x.size()
#define ALL(x) (x).begin(), (x).end()
#define ALLR(x) (x).rbegin(), (x).rend()
#define VE vector<ll>
#define COUT(x) cout << (x) << endl
#define MA map<ll, ll>
#define SE set<ll>
#define PQ priority_queue<ll>
#define PQR priority_queue<ll, VE, greater<ll>>
#define COUT(x) cout << (x) << endl
#define YES(n) cout << ((n) ? "YES" : "NO") << endl
#define Yes(n) cout << ((n) ? "Yes" : "No") << endl
#define EPS (1e-10)
ll gcd(ll a, ll b) {
  if (a < b)
    swap(a, b);
  if (b == 0)
    return a;
  return gcd(b, a % b);
}
ll lcm(ll a, ll b) {
  ll g = gcd(a, b);
  return a / g * b;
}
bool prime(ll n) {
  for (ll i = 2; i <= sqrt(n); i++) {
    if (n % i == 0)
      return false;
  }
  return n != 1;
}

const long long MOD = 1000000007;
const long long INF = 1LL << 60;

const int MAX_N = 100010;
bool used[MAX_N];
signed main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  int n;
  cin >> n;
  // グラフ
  vector<VE> G(n);
  vector<P> vp;
  rep(i, n) {
    int a, b;
    cin >> a >> b;
    a--;
    b--;
    G[a].push_back(b);
    G[b].push_back(a);
    vp.push_back(make_pair(a, b));
  }
  // 色の数
  int k = 0;
  vector<int> hennoiro(n); // その名の通り
  map<P, int> I;           // 出力用map
  // 幅優先探索
  queue<int> que;
  used[0] = true;
  que.emplace(0);
  while (!que.empty()) {
    int v = que.front();
    que.pop();
    chmax(k, (int)G[v].size());
    int color = 1;
    for (int u : G[v]) {
      if (used[u])
        continue;
      if (color == hennoiro[v])
        color++;
      hennoiro[u] = I[make_pair(u, v)] = I[make_pair(v, u)] = color++;
      used[u] = true;
      que.emplace(u);
    }
  }
  cout << k << endl;
  for (auto p : vp)
    cout << I[p] << endl;
  return 0;
}


Fixed submission:
#include <algorithm>
#include <bitset>
#include <cfloat>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <deque>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <limits.h>
#include <list>
#include <map>
#include <math.h>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}

using namespace std;
#define int long long
#define ll long long
#define rep(i, n) for (ll i = 0; i < (n); i++)
#define FOR(i, a, b) for (ll i = (a); i < (b); i++)
#define FORR(i, a, b) for (ll i = (a); i <= (b); i++)
#define repr(i, n) for (ll i = n; i >= 0; i--)
#define P pair<ll, ll>
#define sz(x) (ll) x.size()
#define ALL(x) (x).begin(), (x).end()
#define ALLR(x) (x).rbegin(), (x).rend()
#define VE vector<ll>
#define COUT(x) cout << (x) << endl
#define MA map<ll, ll>
#define SE set<ll>
#define PQ priority_queue<ll>
#define PQR priority_queue<ll, VE, greater<ll>>
#define COUT(x) cout << (x) << endl
#define YES(n) cout << ((n) ? "YES" : "NO") << endl
#define Yes(n) cout << ((n) ? "Yes" : "No") << endl
#define EPS (1e-10)
ll gcd(ll a, ll b) {
  if (a < b)
    swap(a, b);
  if (b == 0)
    return a;
  return gcd(b, a % b);
}
ll lcm(ll a, ll b) {
  ll g = gcd(a, b);
  return a / g * b;
}
bool prime(ll n) {
  for (ll i = 2; i <= sqrt(n); i++) {
    if (n % i == 0)
      return false;
  }
  return n != 1;
}

const long long MOD = 1000000007;
const long long INF = 1LL << 60;

const int MAX_N = 100010;
bool used[MAX_N];
signed main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  int n;
  cin >> n;
  // グラフ
  vector<VE> G(n);
  vector<P> vp;
  rep(i, n - 1) {
    int a, b;
    cin >> a >> b;
    a--;
    b--;
    G[a].push_back(b);
    G[b].push_back(a);
    vp.push_back(make_pair(a, b));
  }
  // 色の数
  int k = 0;
  vector<int> hennoiro(n); // その名の通り
  map<P, int> I;           // 出力用map
  // 幅優先探索
  queue<int> que;
  used[0] = true;
  que.emplace(0);
  while (!que.empty()) {
    int v = que.front();
    que.pop();
    chmax(k, (int)G[v].size());
    int color = 1;
    for (int u : G[v]) {
      if (used[u])
        continue;
      if (color == hennoiro[v])
        color++;
      hennoiro[u] = I[make_pair(u, v)] = I[make_pair(v, u)] = color++;
      used[u] = true;
      que.emplace(u);
    }
  }
  cout << k << endl;
  for (auto p : vp)
    cout << I[p] << endl;
  return 0;
}