Problem p02584 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>

using namespace std;

#define gc getchar_unlocked
#define foi(i, n) for (int i = 0; i < n; i++)
#define Foi(i, k, n)                                                           \
  for (int i = k; k < n ? i < n : i > n; k < n ? i += 1 : i -= 1)
#define fol(i, n) for (ll i = 0; i < n; i++)
#define Fol(i, k, n)                                                           \
  for (ll i = k; k < n ? i < n : i > n; k < n ? i += 1 : i -= 1)
#define ll long long
#define si(x) scanf("%d", &x)
#define sl(x) scanf("%lld", &x)
#define ss(s) scanf("%s", s)
#define pi(x) printf("%d\n", x)
#define pl(x) printf("%lld\n", x)
#define ps(s) printf("%s\n", s)
#define deb(x) cout << #x << "=" << x << endl
#define deb2(x, y) cout << #x << "=" << x << "," << #y << "=" << y << endl
#define pb push_back
#define mp make_pair
#define F first
#define S second
#define all(x) x.begin(), x.end()
#define clr(x) memset(x, 0, sizeof(x))
#define sortall(x) sort(all(x))
#define tr(it, a) for (auto it = a.begin(); it != a.end(); it++)
#define PI 3.1415926535897932384626
typedef pair<int, int> pii;
typedef pair<ll, ll> pl;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<pii> vpii;
typedef vector<pl> vpl;
typedef vector<vi> vvi;
typedef vector<vl> vvl;
int mpow(int base, int exp);
void ipgraph(int m);
void dfs(int u, int par);
const int mod = 1000000007;
const int N = 3e5, M = N;
//=======================

vi g[N];
int a[N];

int mpow(int base, int exp) {
  base %= mod;
  int result = 1;
  while (exp > 0) {
    if (exp & 1)
      result = ((ll)result * base) % mod;
    base = ((ll)base * base) % mod;
    exp >>= 1;
  }
  return result;
}

void ipgraph(int n, int m) {
  int i, u, v;
  while (m--) {
    cin >> u >> v;
    g[u - 1].pb(v - 1);
    g[v - 1].pb(u - 1);
  }
}

void dfs(int u, int par) {
  for (int v : g[u]) {
    if (v == par)
      continue;
    dfs(v, u);
  }
}

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long x, k, d;
  cin >> x >> k >> d;
  x = abs(x);
  while (k--) {
    x -= d;
    if (x - d < 0)
      break;
  }
  if (k % 2 && k > 0)
    x = min(x + d, abs(x - d));
  cout << abs(x);
  return 0;
}

Fixed submission:
#include <bits/stdc++.h>

using namespace std;

#define gc getchar_unlocked
#define foi(i, n) for (int i = 0; i < n; i++)
#define Foi(i, k, n)                                                           \
  for (int i = k; k < n ? i < n : i > n; k < n ? i += 1 : i -= 1)
#define fol(i, n) for (ll i = 0; i < n; i++)
#define Fol(i, k, n)                                                           \
  for (ll i = k; k < n ? i < n : i > n; k < n ? i += 1 : i -= 1)
#define ll long long
#define si(x) scanf("%d", &x)
#define sl(x) scanf("%lld", &x)
#define ss(s) scanf("%s", s)
#define pi(x) printf("%d\n", x)
#define pl(x) printf("%lld\n", x)
#define ps(s) printf("%s\n", s)
#define deb(x) cout << #x << "=" << x << endl
#define deb2(x, y) cout << #x << "=" << x << "," << #y << "=" << y << endl
#define pb push_back
#define mp make_pair
#define F first
#define S second
#define all(x) x.begin(), x.end()
#define clr(x) memset(x, 0, sizeof(x))
#define sortall(x) sort(all(x))
#define tr(it, a) for (auto it = a.begin(); it != a.end(); it++)
#define PI 3.1415926535897932384626
typedef pair<int, int> pii;
typedef pair<ll, ll> pl;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<pii> vpii;
typedef vector<pl> vpl;
typedef vector<vi> vvi;
typedef vector<vl> vvl;
int mpow(int base, int exp);
void ipgraph(int m);
void dfs(int u, int par);
const int mod = 1000000007;
const int N = 3e5, M = N;
//=======================

vi g[N];
int a[N];

int mpow(int base, int exp) {
  base %= mod;
  int result = 1;
  while (exp > 0) {
    if (exp & 1)
      result = ((ll)result * base) % mod;
    base = ((ll)base * base) % mod;
    exp >>= 1;
  }
  return result;
}

void ipgraph(int n, int m) {
  int i, u, v;
  while (m--) {
    cin >> u >> v;
    g[u - 1].pb(v - 1);
    g[v - 1].pb(u - 1);
  }
}

void dfs(int u, int par) {
  for (int v : g[u]) {
    if (v == par)
      continue;
    dfs(v, u);
  }
}

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long x, k, d;
  cin >> x >> k >> d;
  x = abs(x);
  ll quo = x / d;
  if (quo < k) {
    k -= quo;
    x %= d;
  } else {
    x -= k * d;
    k = 0;
  }
  if (k % 2 && k > 0)
    x = min(x + d, abs(x - d));
  cout << abs(x);
  return 0;
}