Problem p02698 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <algorithm>
#include <array>
#include <cassert>
#include <climits>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
using namespace std;
typedef long long ll;
#define REP(i, n) for (int i = 0; i < (int)(n); ++i)
#define FOR(i, a, b) for (int i = (a); i < (int)(b); ++i)
#define ALL(c) (c).begin(), (c).end()
#define SIZE(v) ((int)v.size())
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;
}
template <int MOD> struct Fp {
  ll val;
  constexpr Fp(ll v = 0) noexcept : val(v % MOD) {
    if (val < 0)
      val += MOD;
  }
  constexpr int getmod() { return MOD; }
  constexpr Fp operator-() const noexcept { return val ? MOD - val : 0; }
  constexpr Fp operator+(const Fp &r) const noexcept { return Fp(*this) += r; }
  constexpr Fp operator-(const Fp &r) const noexcept { return Fp(*this) -= r; }
  constexpr Fp operator*(const Fp &r) const noexcept { return Fp(*this) *= r; }
  constexpr Fp operator/(const Fp &r) const noexcept { return Fp(*this) /= r; }
  constexpr Fp &operator+=(const Fp &r) noexcept {
    val += r.val;
    if (val >= MOD)
      val -= MOD;
    return *this;
  }
  constexpr Fp &operator-=(const Fp &r) noexcept {
    val -= r.val;
    if (val < 0)
      val += MOD;
    return *this;
  }
  constexpr Fp &operator*=(const Fp &r) noexcept {
    val = val * r.val % MOD;
    return *this;
  }
  constexpr Fp &operator/=(const Fp &r) noexcept {
    ll a = r.val, b = MOD, u = 1, v = 0;
    while (b) {
      ll t = a / b;
      a -= t * b;
      swap(a, b);
      u -= t * v;
      swap(u, v);
    }
    val = val * u % MOD;
    if (val < 0)
      val += MOD;
    return *this;
  }
  constexpr bool operator==(const Fp &r) const noexcept {
    return this->val == r.val;
  }
  constexpr bool operator!=(const Fp &r) const noexcept {
    return this->val != r.val;
  }
  friend constexpr ostream &operator<<(ostream &os, const Fp<MOD> &x) noexcept {
    return os << x.val;
  }
  friend constexpr Fp<MOD> modpow(const Fp<MOD> &a, ll n) noexcept {
    if (n == 0)
      return 1;
    auto t = modpow(a, n / 2);
    t = t * t;
    if (n & 1)
      t = t * a;
    return t;
  }
};
constexpr ll MOD = 1e9 + 7;
using mint = Fp<MOD>;

#define pb push_back
#define mp make_pair
#define mt make_tuple

int INF = 1e9 + 10;

vector<int> As;
vector<vector<int>> edges;
vector<int> ans;

void dfs(int v, int par, vector<int> &dp, int local_ans) {
  // cout << "v: " << (v+1) << endl;
  // cout << "dp(before):";
  // for (auto e: dp) cout << e << ","; cout << endl;

  // 蟻本と同じ方法でLIS
  auto it = lower_bound(ALL(dp), As[v]);

  // 配列変更前の値をとっておく
  auto prev_value = *it;

  *it = As[v];

  // cout << "dp(after):";
  // for (auto e: dp) cout << e << ","; cout << endl;

  chmax(local_ans, int(it - dp.begin()) + 1);
  ans[v] = local_ans;

  for (auto u : edges[v]) {
    if (u == par)
      continue;
    dfs(u, v, dp, local_ans);
  }

  // もとに戻す
  *it = prev_value;
}

int main(void) {
  cin.sync_with_stdio(false);
  int N;
  cin >> N;

  As.resize(N);
  edges.resize(N);
  ans.resize(N);

  REP(n, N) cin >> As[n];

  REP(n, N - 1) {
    int u, v;
    cin >> u >> v;
    u--;
    v--;
    edges[u].pb(v);
    edges[v].pb(u);
  }

  vector<int> dp(N, INF);
  dfs(0, -1, dp, 0);
  for (auto a : ans)
    cout << a << endl;

  return 0;
}


Error: TLE

Fixed submission:

#include <algorithm>
#include <array>
#include <cassert>
#include <climits>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
using namespace std;
typedef long long ll;
#define REP(i, n) for (int i = 0; i < (int)(n); ++i)
#define FOR(i, a, b) for (int i = (a); i < (int)(b); ++i)
#define ALL(c) (c).begin(), (c).end()
#define SIZE(v) ((int)v.size())
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;
}
template <int MOD> struct Fp {
  ll val;
  constexpr Fp(ll v = 0) noexcept : val(v % MOD) {
    if (val < 0)
      val += MOD;
  }
  constexpr int getmod() { return MOD; }
  constexpr Fp operator-() const noexcept { return val ? MOD - val : 0; }
  constexpr Fp operator+(const Fp &r) const noexcept { return Fp(*this) += r; }
  constexpr Fp operator-(const Fp &r) const noexcept { return Fp(*this) -= r; }
  constexpr Fp operator*(const Fp &r) const noexcept { return Fp(*this) *= r; }
  constexpr Fp operator/(const Fp &r) const noexcept { return Fp(*this) /= r; }
  constexpr Fp &operator+=(const Fp &r) noexcept {
    val += r.val;
    if (val >= MOD)
      val -= MOD;
    return *this;
  }
  constexpr Fp &operator-=(const Fp &r) noexcept {
    val -= r.val;
    if (val < 0)
      val += MOD;
    return *this;
  }
  constexpr Fp &operator*=(const Fp &r) noexcept {
    val = val * r.val % MOD;
    return *this;
  }
  constexpr Fp &operator/=(const Fp &r) noexcept {
    ll a = r.val, b = MOD, u = 1, v = 0;
    while (b) {
      ll t = a / b;
      a -= t * b;
      swap(a, b);
      u -= t * v;
      swap(u, v);
    }
    val = val * u % MOD;
    if (val < 0)
      val += MOD;
    return *this;
  }
  constexpr bool operator==(const Fp &r) const noexcept {
    return this->val == r.val;
  }
  constexpr bool operator!=(const Fp &r) const noexcept {
    return this->val != r.val;
  }
  friend constexpr ostream &operator<<(ostream &os, const Fp<MOD> &x) noexcept {
    return os << x.val;
  }
  friend constexpr Fp<MOD> modpow(const Fp<MOD> &a, ll n) noexcept {
    if (n == 0)
      return 1;
    auto t = modpow(a, n / 2);
    t = t * t;
    if (n & 1)
      t = t * a;
    return t;
  }
};
constexpr ll MOD = 1e9 + 7;
using mint = Fp<MOD>;

#define pb push_back
#define mp make_pair
#define mt make_tuple

int INF = 1e9 + 10;

vector<int> As;
vector<vector<int>> edges;
vector<int> ans;

void dfs(int v, int par, vector<int> dp, int local_ans) {
  // cout << "v: " << (v+1) << endl;
  // cout << "dp:";
  // for (auto e: dp) cout << e << ","; cout << endl;

  // 蟻本と同じ方法でLIS
  auto it = lower_bound(ALL(dp), As[v]);

  // 配列変更前の値をとっておく
  auto prev_value = As[v];

  *it = As[v];

  chmax(local_ans, int(it - dp.begin()) + 1);
  ans[v] = local_ans;

  for (auto u : edges[v]) {
    if (u == par)
      continue;
    dfs(u, v, dp, local_ans);
  }

  // もとに戻す
  *it = prev_value;
}

int main(void) {
  cin.sync_with_stdio(false);
  int N;
  cin >> N;

  As.resize(N);
  edges.resize(N);
  ans.resize(N);

  REP(n, N) cin >> As[n];

  REP(n, N - 1) {
    int u, v;
    cin >> u >> v;
    u--;
    v--;
    edges[u].pb(v);
    edges[v].pb(u);
  }

  vector<int> dp(N, INF);
  dfs(0, -1, dp, 0);
  for (auto a : ans)
    cout << a << endl;

  return 0;
}