algorithm/baekjoon/8462.cpp at master · highalps/algorithm · GitHub

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/*
8462
Sqrt decomposition, Mo's algorithm
http://highalps.tistory.com/11
*/

#include <math.h>
#include <stdio.h>
#include <stdlib.h>

#include <algorithm>
#include <vector>
using namespace std;
#define ll long long
int h;
struct dot {
  int l, r, id;
  bool operator<(const dot& A) const {
    return l / h == A.l / h ? r < A.r : l / h < A.l / h;
  }
} query[100001];
ll res[100001];
int cnt[1000001];
ll move(int t, int val) {
  cnt[val] += t;
  return ((ll)2 * (ll)t * (ll)cnt[val] - 1) * (ll)val;
}
int main() {
  int n, k, l, r;
  scanf("%d %d", &n, &k);
  h = sqrt(n);
  vector<ll> a(n + 1, 0);
  for (int i = 1; i <= n; i++) scanf("%lld", &a[i]);
  for (int i = 0; i < k; i++) {
    scanf("%d %d", &query[i].l, &query[i].r);
    query[i].id = i;
  }
  sort(query, query + k);

  ll sum = 0;
  l = query[0].l, r = query[0].r;
  for (int i = l; i <= r; i++) sum += move(1, a[i]);
  res[query[0].id] = sum;

  for (int i = 1; i < k; i++) {
    while (l > query[i].l) sum += move(1, a[--l]);
    while (l < query[i].l) sum += move(-1, a[l++]);
    while (r > query[i].r) sum += move(-1, a[r--]);
    while (r < query[i].r) sum += move(1, a[++r]);
    res[query[i].id] = sum;
  }
  for (int i = 0; i < k; i++) printf("%lld\n", res[i]);
  return 0;
}