Problem p02548 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
#define int long long
#define endl '\n'
#define mod 1000000007
#define inf 1e18
#define PI 3.14159265358979323846264338327950L
#define w(x)                                                                   \
  int x;                                                                       \
  cin >> x;                                                                    \
  while (x--)
using namespace std;
bool sieve[2000006];
void sieve_make() {
  memset(sieve, true, sizeof(sieve));
  sieve[0] = sieve[1] = false;
  for (int i = 2; i * i < 2000006; i++) {
    if (sieve[i]) {
      for (int j = i * i; j < 2000006; j += i)
        sieve[j] = false;
    }
  }
}

int max(int a, int b) {
  if (a > b)
    return a;
  return b;
}
int min(int a, int b) {
  if (a < b)
    return a;
  return b;
}
int modexp(int a, int b, int c) {
  if (a == 0)
    return 0;
  if (b == 0)
    return 1;

  int ans;
  if (b % 2 == 0) {
    int small = modexp(a, b / 2, c);
    ans = (small * small) % c;
  } else {
    int small = modexp(a, b - 1, c);
    ans = (a % c);
    ans = (small * ans) % c;
  }
  return (ans + c) % c;
}
bool sign(int x) {
  if (x > 0)
    return true;
  return false;
}
int kadane(int *a, int n) {
  int loc = a[0], glo = a[0];
  for (int i = 1; i < n; i++) {
    loc = max(a[i], loc + a[i]);
    glo = max(glo, loc);
  }
  return glo;
}

int dp[100005];
int dfs(vector<int> *adj, int sv, bool col, bool *vis, int n) {
  if (sv == n - 1)
    return 1;

  int ans = 0;
  for (auto i : adj[sv]) {
    if (!vis[i]) {
      vis[i] = 1;
      if (col)
        ans += dfs(adj, i, !col, vis, n);
      else
        ans += dfs(adj, i, !col, vis, n) + dfs(adj, i, col, vis, n);
      vis[i] = 0;
    }
  }
  return ans;
}

int32_t main() {
  ios::sync_with_stdio(NULL);
  cin.tie(NULL);
  cout.tie(NULL);

  int n;
  cin >> n;

  int ans = 0;
  for (int i = 1; i < n; i++) {
    int temp = n - i, j;

    for (j = 1; j * j <= temp; j++) {
      if (j * j == temp)
        ans++;
      else if (temp % j == 0)
        ans += 2;
    }
  }
  cout << ans << endl;
}


Fixed submission:
#include <bits/stdc++.h>
#define int long long
#define endl '\n'
#define mod 1000000007
#define inf 1e18
#define PI 3.14159265358979323846264338327950L
#define w(x)                                                                   \
  int x;                                                                       \
  cin >> x;                                                                    \
  while (x--)
using namespace std;
bool sieve[2000006];
void sieve_make() {
  memset(sieve, true, sizeof(sieve));
  sieve[0] = sieve[1] = false;
  for (int i = 2; i * i < 2000006; i++) {
    if (sieve[i]) {
      for (int j = i * i; j < 2000006; j += i)
        sieve[j] = false;
    }
  }
}

int max(int a, int b) {
  if (a > b)
    return a;
  return b;
}
int min(int a, int b) {
  if (a < b)
    return a;
  return b;
}
int modexp(int a, int b, int c) {
  if (a == 0)
    return 0;
  if (b == 0)
    return 1;

  int ans;
  if (b % 2 == 0) {
    int small = modexp(a, b / 2, c);
    ans = (small * small) % c;
  } else {
    int small = modexp(a, b - 1, c);
    ans = (a % c);
    ans = (small * ans) % c;
  }
  return (ans + c) % c;
}
bool sign(int x) {
  if (x > 0)
    return true;
  return false;
}
int kadane(int *a, int n) {
  int loc = a[0], glo = a[0];
  for (int i = 1; i < n; i++) {
    loc = max(a[i], loc + a[i]);
    glo = max(glo, loc);
  }
  return glo;
}

int dp[100005];
int dfs(vector<int> *adj, int sv, bool col, bool *vis, int n) {
  if (sv == n - 1)
    return 1;

  int ans = 0;
  for (auto i : adj[sv]) {
    if (!vis[i]) {
      vis[i] = 1;
      if (col)
        ans += dfs(adj, i, !col, vis, n);
      else
        ans += dfs(adj, i, !col, vis, n) + dfs(adj, i, col, vis, n);
      vis[i] = 0;
    }
  }
  return ans;
}

int32_t main() {
  ios::sync_with_stdio(NULL);
  cin.tie(NULL);
  cout.tie(NULL);

  int n;
  cin >> n;

  int ans = 0;
  for (int i = 1; i < n; i++) {
    ans += (n - 1) / i;
  }
  cout << ans << endl;
}