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

/*      西江月·证明
        即得易见平凡，仿照上例显然。
   留作习题答案略， 读者自证不难。

        反之亦然同理，推论自然成立。
        略去过程QED，由上可知证毕。*/
#pragma GCC optimize(1)
#pragma GCC optimize(2)
#pragma GCC optimize(3)
#pragma GCC optimize("Ofast")
#include <algorithm>
#include <cstdio>
#include <iostream>
#include <queue>
#define kkk register
#define ll long long
#define inf 2147098934832ll
using namespace std;
ll read() {
  ll ans = 0, f = 1;
  char a = getchar();
  while (a > '9' || a < '0') {
    if (a == '-')
      f = -1;
    a = getchar();
  }
  while (a >= '0' && a <= '9')
    ans = (ans << 3) + (ans << 1) + a - '0', a = getchar();
  return ans * f;
}
// 一条long
// long的黄金分割线-----------------------------------------------------------------------------------------------------------------------------------
ll a[2000005], n, m, sum, x;
int main() {
  n = read();
  for (int i = 1; i <= n; i++)
    x = read(), a[x]++, sum += x;
  m = read();
  for (int i = 1; i <= m; i++) {
    ll b = read(), c = read();
    sum += a[b] * (c - b);
    a[c] += a[b];
    a[b] = 0;
    printf("%lld\\n", sum);
  }
  return 0;
}

Error: TLE

Fixed submission:

#include <bits/stdc++.h>
#pragma GCC optimize(2)
#pragma GCC optimize(3)
#pragma GCC optimize("Ofast")
#pragma GCC optimize("inline")
#pragma GCC optimize("-fgcse")
#pragma GCC optimize("-fgcse-lm")
#pragma GCC optimize("-fipa-sra")
#pragma GCC optimize("-ftree-pre")
#pragma GCC optimize("-ftree-vrp")
#pragma GCC optimize("-fpeephole2")
#pragma GCC optimize("-ffast-math")
#pragma GCC optimize("-fsched-spec")
#pragma GCC optimize("unroll-loops")
#pragma GCC optimize("-falign-jumps")
#pragma GCC optimize("-falign-loops")
#pragma GCC optimize("-falign-labels")
#pragma GCC optimize("-fdevirtualize")
#pragma GCC optimize("-fcaller-saves")
#pragma GCC optimize("-fcrossjumping")
#pragma GCC optimize("-fthread-jumps")
#pragma GCC optimize("-funroll-loops")
#pragma GCC optimize("-fwhole-program")
#pragma GCC optimize("-freorder-blocks")
#pragma GCC optimize("-fschedule-insns")
#pragma GCC optimize("inline-functions")
#pragma GCC optimize("-ftree-tail-merge")
#pragma GCC optimize("-fschedule-insns2")
#pragma GCC optimize("-fstrict-aliasing")
#pragma GCC optimize("-fstrict-overflow")
#pragma GCC optimize("-falign-functions")
#pragma GCC optimize("-fcse-skip-blocks")
#pragma GCC optimize("-fcse-follow-jumps")
#pragma GCC optimize("-fsched-interblock")
#pragma GCC optimize("-fpartial-inlining")
#pragma GCC optimize("no-stack-protector")
#pragma GCC optimize("-freorder-functions")
#pragma GCC optimize("-findirect-inlining")
#pragma GCC optimize("-fhoist-adjacent-loads")
#pragma GCC optimize("-frerun-cse-after-loop")
#pragma GCC optimize("inline-small-functions")
#pragma GCC optimize("-finline-small-functions")
#pragma GCC optimize("-ftree-switch-conversion")
#pragma GCC optimize("-foptimize-sibling-calls")
#pragma GCC optimize("-fexpensive-optimizations")
#pragma GCC optimize("-funsafe-loop-optimizations")
#pragma GCC optimize("inline-functions-called-once")
#pragma GCC optimize("-fdelete-null-pointer-checks")

using namespace std;

int main() {
  int n;
  scanf("%d", &n);
  int a[100086];
  for (int i = 1; i <= n; i++)
    scanf("%d", &a[i]);
  int q;
  scanf("%d", &q);
  for (int i = 1; i <= q; i++) {
    int u, v;
    scanf("%d%d", &u, &v);
    int ans = 0;
    for (int j = 1; j <= n; j++) {
      if (a[j] == u)
        a[j] = v;
      ans += a[j];
    }
    printf("%d\\n", ans);
  }
  return 0;
}