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

#include <bits/stdc++.h>
using namespace std;
#define SORT(c) sort((c).begin(), (c).end());
#define pb push_back
#define MP make_pair
#define pii pair<int, int>
#define pcc pair<char, char>
#define pic pair<int, char>
#define pci pair<char, int>
#define VS vector<string>
#define VI vector<int>
#define pi 3.141592653589793
#define ll long long
#define ull unsigned long long
#define w(x)                                                                   \\
  int x;                                                                       \\
  cin >> x;                                                                    \\
  while (x--)
#define fast ios_base::sync_with_stdio(0)
#define sz size()
#define cu cout <<
#define en endl
#define sp " "
#include <cstdio>
#include <cstring>
typedef unsigned long long UL;
template <typename T> inline T S(T a) { return a * a; }
template <class T> inline string tostring(T a) {
  ostringstream os("");
  os << a;
  return os.str();
}
template <typename T> inline ll tolong(T a) {
  ll res;
  istringstream os(a);
  os >> res;
  return res;
}
template <typename T> inline T gcd(T a, T b) {
  if (b == 0)
    return a;
  else
    return gcd(b, a % b);
}
template <typename T> inline T bigmod(T a, T b, T m) {
  if (b == 0)
    return 1;
  else if (b % 2 == 0)
    return S(bigmod(a, b / 2, m)) % m;
  else
    return (a % m * bigmod(a, b - 1, m)) % m;
}
const int inf = (int)1e9 + 5;
const ll linf = (ll)1e16 + 5;
const ll modd = (ll)1e9 + 7;
const int mod = 10000007;
/*#define N 20000009
bool prime[N];
vector<ll> prm;
void seive ()
{

    memset(prime, true, sizeof(prime));

    for( ll i=2; i*i<=N; i++)
    {
        if (prime[i] == true)
        {
            prm.pb(i);
            for (ll j=i*i; j<=N; j += i)
                pe[j] = false;
        }
    }
}*/
void pr(int f) {
  if (f == 1)
    cout << "YES\\n";
  else
    cout << "NO\\n";
}
bool isprime(ll n) {
  if (n < 2)
    return 0;
  if (n == 2)
    return 1;
  else {
    for (int i = 2; i * i <= n; i++)
      if (n % i == 0)
        return 0;
  }
  return 1;
}
map<int, int> mp;
set<int> st;
multiset<string>::iterator it;
deque<char> q;
int vis[10000000];
pair<int, int> a[2020];
int main() {
  fast;
  ll n;
  cin >> n;

  map<ll, ll> m;
  ll c = 0;
  for (int i = 1; i <= n; i++) {
    ll f;
    cin >> f;
    m[f]++;
    c += f;
  }
  w(t) {
    ll a, b;
    cin >> a >> b;
    c -= m[a] * a;
    c += m[a] * b;
    m[b] += m[a];
    m[a] = 0;
    cout << c << endl;
  }
}


Error: TLE

Fixed submission:

#include <bits/stdc++.h>
using namespace std;
#define SORT(c) sort((c).begin(), (c).end());
#define pb push_back
#define MP make_pair
#define pii pair<int, int>
#define pcc pair<char, char>
#define pic pair<int, char>
#define pci pair<char, int>
#define VS vector<string>
#define VI vector<int>
#define pi 3.141592653589793
#define ll long long
#define ull unsigned long long
#define w(x)                                                                   \\
  int x;                                                                       \\
  cin >> x;                                                                    \\
  while (x--)
#define fast ios_base::sync_with_stdio(0)
#define sz size()
#define cu cout <<
#define en endl
#define sp " "
#include <cstdio>
#include <cstring>
typedef unsigned long long UL;
template <typename T> inline T S(T a) { return a * a; }
template <class T> inline string tostring(T a) {
  ostringstream os("");
  os << a;
  return os.str();
}
template <typename T> inline ll tolong(T a) {
  ll res;
  istringstream os(a);
  os >> res;
  return res;
}
template <typename T> inline T gcd(T a, T b) {
  if (b == 0)
    return a;
  else
    return gcd(b, a % b);
}
template <typename T> inline T bigmod(T a, T b, T m) {
  if (b == 0)
    return 1;
  else if (b % 2 == 0)
    return S(bigmod(a, b / 2, m)) % m;
  else
    return (a % m * bigmod(a, b - 1, m)) % m;
}
const int inf = (int)1e9 + 5;
const ll linf = (ll)1e16 + 5;
const ll modd = (ll)1e9 + 7;
const int mod = 10000007;
/*#define N 20000009
bool prime[N];
vector<ll> prm;
void seive ()
{

    memset(prime, true, sizeof(prime));

    for( ll i=2; i*i<=N; i++)
    {
        if (prime[i] == true)
        {
            prm.pb(i);
            for (ll j=i*i; j<=N; j += i)
                pe[j] = false;
        }
    }
}*/
void pr(int f) {
  if (f == 1)
    cout << "YES\\n";
  else
    cout << "NO\\n";
}
bool isprime(ll n) {
  if (n < 2)
    return 0;
  if (n == 2)
    return 1;
  else {
    for (int i = 2; i * i <= n; i++)
      if (n % i == 0)
        return 0;
  }
  return 1;
}
map<int, int> mp;
set<int> st;
multiset<string>::iterator it;
deque<char> q;
int vis[10000000];
pair<int, int> a[2020];
int main() {
  fast;
  int n;
  cin >> n;
  int ar[n + 1];
  for (int i = 1; i <= n; i++)
    cin >> ar[i];
  w(t) {
    int a, b;
    cin >> a >> b;
    int sum = 0;
    for (int i = 1; i <= n; i++) {
      if (ar[i] == a) {
        sum += b;
        ar[i] = b;
      } else
        sum += ar[i];
    }

    cout << sum << endl;
  }
}