Problem p02630 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <bits/stdc++.h>

using namespace std;
using ll = long long int;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using vi = vector<int>;
using vl = vector<ll>;
using vb = vector<bool>;
using vs = vector<string>;
using vvi = vector<vector<int>>;
using vvl = vector<vector<ll>>;
using vvb = vector<vector<bool>>;
using vvs = vector<vector<string>>;
template <typename T> using vv = vector<vector<T>>;
template <typename T> using vvv = vector<vector<vector<T>>>;
template <typename T> using pq = priority_queue<T>;
template <typename T> using pqg = priority_queue<T, vector<T>, greater<T>>;

const int INF = 1e9;
const ll LINF = 1e18;
const ll MOD = 1e9 + 7;
const int DX[4] = {1, 0, -1, 0};
const int DY[4] = {0, 1, 0, -1};

#define _sel(_1, _2, x, ...) x
#define repn(i, n) for (ll i = 0; i < (n); i++)
#define reps(i, a, b) for (ll i = (a); i < (b); i++)
#define rep(i, ...) _sel(__VA_ARGS__, reps, repn)(i, __VA_ARGS__)
#define reppn(i, n) for (ll i = 1; i <= (n); i++)
#define repps(i, a, b) for (ll i = (a); i <= (b); i++)
#define repp(i, ...) _sel(__VA_ARGS__, repps, reppn)(i, __VA_ARGS__)
#define rrepn(i, n) for (ll i = (n)-1; i >= 0; i--)
#define rreps(i, a, b) for (ll i = (b)-1; i >= (a); i--)
#define rrep(i, ...) _sel(__VA_ARGS__, rreps, rrepn)(i, __VA_ARGS__)
#define rreppn(i, n) for (ll i = (n); i >= 1; i--)
#define rrepps(i, a, b) for (ll i = (b); i >= (a); i--)
#define rrepp(i, ...) _sel(__VA_ARGS__, rrepps, rreppn)(i, __VA_ARGS__)

#define pb push_back
#define mp make_pair
#define mt make_tuple
#define fi first
#define se second
#define rng(v) (v).begin(), (v).end()
#define rrng(v) (v).rbegin(), (v).rend()
#define siz(x) int((x).size())
#define pow2(x) (1ll << (x))
#define bit(x, n) ((x) >> (n)&1)
#define prt(x) cout << (x) << endl
#define dbg(x) dbgn(#x, x)

template <typename T, typename U> inline bool umax(T &m, U x) {
  if (m < x) {
    m = x;
    return true;
  }
  return false;
}
template <typename T, typename U> inline bool umin(T &m, U x) {
  if (m > x) {
    m = x;
    return true;
  }
  return false;
}
template <typename T> inline void errv(T &v) {
  for (auto x : v)
    cerr << x << " ";
  cerr << endl;
}
inline void errv(vb &v) {
  for (auto x : v)
    cerr << (x ? 1 : 0) << " ";
  cerr << endl;
}
template <typename T> inline void dbgn(string n, T x) {
  cerr << n << ": " << x << endl;
}
template <typename T> inline void dbgn(string n, vector<T> &v) {
  cerr << n << ": ";
  errv(v);
}
template <typename T> inline void dbgn(string n, vv<T> &m) {
  cerr << n << ":" << endl;
  for (auto &v : m)
    errv(v);
}

int main() {
  ll n;
  cin >> n;
  map<ll, ll> a;
  rep(i, n) {
    ll t;
    cin >> t;
    if (a.count(t) == 0) {
      a[t] = 1;
    } else {
      a[t]++;
    }
  }

  ll q;
  cin >> q;

  ll sum = 0;
  for (auto t : a) {
    sum += t.fi * t.se;
  }

  rep(i, q) {
    ll b, c;
    cin >> b >> c;

    if (a.count(b) > 0) {
      sum -= b * a[b];
      sum += c * a[b];
      if (a.count(c) == 0) {
        a[c] = a[b];
      } else {
        a[c] += a[b];
      }
      a[b] = 0;
    }

    prt(sum);
  }

  return 0;
}


Error: TLE

Fixed submission:

#include <bits/stdc++.h>

using namespace std;
using ll = long long int;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using vi = vector<int>;
using vl = vector<ll>;
using vb = vector<bool>;
using vs = vector<string>;
using vvi = vector<vector<int>>;
using vvl = vector<vector<ll>>;
using vvb = vector<vector<bool>>;
using vvs = vector<vector<string>>;
template <typename T> using vv = vector<vector<T>>;
template <typename T> using vvv = vector<vector<vector<T>>>;
template <typename T> using pq = priority_queue<T>;
template <typename T> using pqg = priority_queue<T, vector<T>, greater<T>>;

const int INF = 1e9;
const ll LINF = 1e18;
const ll MOD = 1e9 + 7;
const int DX[4] = {1, 0, -1, 0};
const int DY[4] = {0, 1, 0, -1};

#define _sel(_1, _2, x, ...) x
#define repn(i, n) for (ll i = 0; i < (n); i++)
#define reps(i, a, b) for (ll i = (a); i < (b); i++)
#define rep(i, ...) _sel(__VA_ARGS__, reps, repn)(i, __VA_ARGS__)
#define reppn(i, n) for (ll i = 1; i <= (n); i++)
#define repps(i, a, b) for (ll i = (a); i <= (b); i++)
#define repp(i, ...) _sel(__VA_ARGS__, repps, reppn)(i, __VA_ARGS__)
#define rrepn(i, n) for (ll i = (n)-1; i >= 0; i--)
#define rreps(i, a, b) for (ll i = (b)-1; i >= (a); i--)
#define rrep(i, ...) _sel(__VA_ARGS__, rreps, rrepn)(i, __VA_ARGS__)
#define rreppn(i, n) for (ll i = (n); i >= 1; i--)
#define rrepps(i, a, b) for (ll i = (b); i >= (a); i--)
#define rrepp(i, ...) _sel(__VA_ARGS__, rrepps, rreppn)(i, __VA_ARGS__)

#define pb push_back
#define mp make_pair
#define mt make_tuple
#define fi first
#define se second
#define rng(v) (v).begin(), (v).end()
#define rrng(v) (v).rbegin(), (v).rend()
#define siz(x) int((x).size())
#define pow2(x) (1ll << (x))
#define bit(x, n) ((x) >> (n)&1)
#define prt(x) cout << (x) << endl
#define dbg(x) dbgn(#x, x)

template <typename T, typename U> inline bool umax(T &m, U x) {
  if (m < x) {
    m = x;
    return true;
  }
  return false;
}
template <typename T, typename U> inline bool umin(T &m, U x) {
  if (m > x) {
    m = x;
    return true;
  }
  return false;
}
template <typename T> inline void errv(T &v) {
  for (auto x : v)
    cerr << x << " ";
  cerr << endl;
}
inline void errv(vb &v) {
  for (auto x : v)
    cerr << (x ? 1 : 0) << " ";
  cerr << endl;
}
template <typename T> inline void dbgn(string n, T x) {
  cerr << n << ": " << x << endl;
}
template <typename T> inline void dbgn(string n, vector<T> &v) {
  cerr << n << ": ";
  errv(v);
}
template <typename T> inline void dbgn(string n, vv<T> &m) {
  cerr << n << ":" << endl;
  for (auto &v : m)
    errv(v);
}

int main() {
  int n;
  cin >> n;
  multiset<int> a;
  rep(i, n) {
    int t;
    cin >> t;
    a.insert(t);
  }

  int q;
  cin >> q;

  ll sum = 0;
  for (auto t : a)
    sum += t;

  rep(i, q) {
    int b, c;
    cin >> b >> c;

    auto cnt = a.erase(b);
    sum -= b * cnt;
    sum += c * cnt;
    rep(i, cnt) a.insert(c);

    prt(sum);
  }

  return 0;
}