Problem p02973 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
#define rep(i, n) for (int64_t i = 0; i < (int64_t)(n); i++)
#define invrep(i, n) for (int64_t i = n - 1; i >= 0; i--)
using namespace std;

//////全探索したいときに開けよ////////
vector<vector<int>> fspattern;
vector<int> fspattern_draft;
int fspcnt = 0;

void setfspattern_core(int floor, int number, int degree) {
  if (floor == degree) {
    fspattern.at(fspcnt) = fspattern_draft;
    fspcnt++;
  } else {
    rep(i, number) {
      fspattern_draft.at(floor) = i;
      setfspattern_core(floor + 1, number, degree);
    }
  }
}

void setfspattern(int number, int degree) {
  fspcnt = 0;
  int64_t array_num = 1;
  rep(i, degree) { array_num *= number; }
  fspattern = vector<vector<int>>(array_num, vector<int>(degree));
  fspattern_draft = vector<int>(degree);
  setfspattern_core(0, number, degree);
}

//////nCrのmodを求めたいときに開けよ/////////
// int64_t univMod = 1000000007;
// int64_t factnum = 100000
// vector<int64_t> modfact(factnum);
// vector<int64_t> modinvfact(factnum);

/*void setmodfact(){
  for(int i=0;i<factnum;i++){
    if(i == 0){
      modfact.at(i) = 1;
    }else{
      modfact.at(i) = (modfact.at(i-1)*i)%univMod;
    }
  }
}

int64_t calcmodpower(int64_t a,int64_t n){
  int64_t res = 1;
  while(n != 0){
    if(n & 1){
      res = (res * a) % univMod;
    }
    a = (a*a) % univMod;
    n = n >> 1;
  }
  return res;
}

int64_t calcinverse(int64_t n){
        return calcmodpower(n,univMod-2);
}

void setmodinvfact(){
  for(int i=0;i<factnum;i++){
    if(i==0){
      modinvfact.at(i) = 1;
    }else{
      modinvfact.at(i) = calcmodpower(modfact.at(i),univMod-2);
    }
  }
}*/

/*
int64_t calcGCD(int64_t a,int64_t b){
        int64_t p = a;
        int64_t q = b;
        int64_t c = a%b;
        while(c != 0){
                p = q;
                q = c;
                c = p%q;
        }
        return q;
}
*/

int main() {
  int64_t n;
  cin >> n;
  vector<int64_t> a(n);
  rep(i, n) { cin >> a.at(i); }
  multiset<int64_t> ms;
  rep(i, n) {
    auto itr = lower_bound(ms.begin(), ms.end(), a.at(i)); // logn
    if (itr == ms.begin()) {
      ms.insert(a.at(i));
      // printf("+%ld",a.at(i));
    } else {
      --itr;
      ms.erase(itr);
      ms.insert(a.at(i));
    }
  }
  cout << ms.size() << endl;
}

Fixed submission:
#include <bits/stdc++.h>
#define rep(i, n) for (int64_t i = 0; i < (int64_t)(n); i++)
#define invrep(i, n) for (int64_t i = n - 1; i >= 0; i--)
using namespace std;

//////全探索したいときに開けよ////////
vector<vector<int>> fspattern;
vector<int> fspattern_draft;
int fspcnt = 0;

void setfspattern_core(int floor, int number, int degree) {
  if (floor == degree) {
    fspattern.at(fspcnt) = fspattern_draft;
    fspcnt++;
  } else {
    rep(i, number) {
      fspattern_draft.at(floor) = i;
      setfspattern_core(floor + 1, number, degree);
    }
  }
}

void setfspattern(int number, int degree) {
  fspcnt = 0;
  int64_t array_num = 1;
  rep(i, degree) { array_num *= number; }
  fspattern = vector<vector<int>>(array_num, vector<int>(degree));
  fspattern_draft = vector<int>(degree);
  setfspattern_core(0, number, degree);
}

//////nCrのmodを求めたいときに開けよ/////////
// int64_t univMod = 1000000007;
// int64_t factnum = 100000
// vector<int64_t> modfact(factnum);
// vector<int64_t> modinvfact(factnum);

/*void setmodfact(){
  for(int i=0;i<factnum;i++){
    if(i == 0){
      modfact.at(i) = 1;
    }else{
      modfact.at(i) = (modfact.at(i-1)*i)%univMod;
    }
  }
}

int64_t calcmodpower(int64_t a,int64_t n){
  int64_t res = 1;
  while(n != 0){
    if(n & 1){
      res = (res * a) % univMod;
    }
    a = (a*a) % univMod;
    n = n >> 1;
  }
  return res;
}

int64_t calcinverse(int64_t n){
        return calcmodpower(n,univMod-2);
}

void setmodinvfact(){
  for(int i=0;i<factnum;i++){
    if(i==0){
      modinvfact.at(i) = 1;
    }else{
      modinvfact.at(i) = calcmodpower(modfact.at(i),univMod-2);
    }
  }
}*/

/*
int64_t calcGCD(int64_t a,int64_t b){
        int64_t p = a;
        int64_t q = b;
        int64_t c = a%b;
        while(c != 0){
                p = q;
                q = c;
                c = p%q;
        }
        return q;
}
*/

int main() {
  int64_t n;
  cin >> n;
  vector<int64_t> a(n);
  rep(i, n) { cin >> a.at(i); }
  multiset<int64_t> ms;
  rep(i, n) {
    auto itr = ms.lower_bound(a.at(i)); // logn
    if (itr == ms.begin()) {
      ms.insert(a.at(i));
      // printf("+%ld",a.at(i));
    } else {
      --itr;
      ms.erase(itr);
      ms.insert(a.at(i));
    }
  }
  cout << ms.size() << endl;
}