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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3. #define fastIO ios_base::sync_with_stdio(0); cin.tie(0);
  4. #define ll long long
  5. #define all(x) x.begin(), x.end()
  6.  
  7. const int INF = 1e9;
  8. const int N = 1e5+5;
  9.  
  10. struct query{
  11.     int l, r, id;
  12. } Q[N];
  13. int n, q, a[N], BLOCK_SIZE, L=1, R=0, cnt[N], res[N];
  14. set<int> se;
  15.  
  16. void solve(int i){
  17.     while (R<Q[i].r){
  18.         R++;
  19.         if (cnt[a[R]]==0){
  20.             se.erase(a[R]);
  21.         }
  22.         cnt[a[R]]++;
  23.     }
  24.     while (L>Q[i].l){
  25.         L--;
  26.         if (cnt[a[L]]==0){
  27.             se.erase(a[L]);
  28.         }
  29.         cnt[a[L]]++;
  30.     }
  31.     while (R>Q[i].r){
  32.         cnt[a[R]]--;
  33.         if (cnt[a[R]]==0){
  34.             se.insert(a[R]);
  35.         }
  36.         R--;
  37.     }
  38.     while (L<Q[i].l){
  39.         cnt[a[L]]--;
  40.         if (cnt[a[L]]==0){
  41.             se.insert(a[L]);
  42.         }
  43.         L++;
  44.     }
  45. }
  46.  
  47. bool MO(query x, query y){
  48.     int X = x.l/BLOCK_SIZE;
  49.     int Y = y.l/BLOCK_SIZE;
  50.  
  51.     if (X!=Y) return X<Y;
  52.     if (X&1) return x.r<y.r;
  53.     return x.r>y.r;
  54. }
  55.  
  56. int main(){
  57.     fastIO;
  58.  
  59.     cin >> n >> q;
  60.     for (int i=1; i<=n; i++) cin >> a[i];
  61.     for (int i=1; i<=q; i++){
  62.         cin >> Q[i].l >> Q[i].r;
  63.         Q[i].id = i;
  64.     }
  65.     BLOCK_SIZE = sqrt(n);
  66.     sort(Q+1, Q+1+q, MO);
  67.     for (int i=1; i<=n; i++) se.insert(i);
  68.     for (int i=1; i<=q; i++){
  69.         solve(i);
  70.         res[Q[i].id] = *(se.begin());
  71.     }
  72.     for (int i=1; i<=q; i++){
  73.         cout << res[i] << '\n';
  74.     }
  75. }
Success #stdin #stdout 0.01s 5320KB
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https://ideone.com/5yaZXZ
language:
C++14 (gcc 8.3)
created:
3 hours ago
visibility:
public

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