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Mo's Algorithm
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// http://codeforces.com/group/kZPk3ZTzR5/contest/101041/problem/D | |
// Nome do problema: Investigating the cartel | |
// Descrição: Quantos elementos com frequência maior que 1 no intervalo | |
// https://www.codepit.io/#/problems/5369c356f6fa9de49e5c7fa3/view | |
// Nome do problema: D-query | |
// Descrição: Quantos elementos diferentes no intervalo | |
// Resolve consultas em O((N+Q)*sqrt(N)+Q*log(Q)) | |
#include <bits/stdc++.h> | |
using namespace std; | |
int n, q, block, tot; | |
int freq[1000006], a[30004]; | |
struct Query { | |
int l, r, idx, bl, ans; | |
}; | |
Query queries[200005]; | |
inline void sub(int i) { | |
tot -= (--freq[a[i]] == 0); | |
} | |
inline void add(int i) { | |
tot += (++freq[a[i]] == 1); | |
} | |
inline void mo() { | |
sort(queries+1, queries+1+q, [](Query a, Query b)->bool { | |
if (a.bl != b.bl) return a.bl < b.bl; | |
return a.r < b.r; | |
}); | |
int l, r, cur_l = 0, cur_r = 0; | |
for (int i = 1; i <= q; i++) { | |
l = queries[i].l; | |
r = queries[i].r; | |
while (cur_l < l) sub(cur_l++); | |
while (cur_l > l) add(--cur_l); | |
while (cur_r < r) add(++cur_r); | |
while (cur_r > r) sub(cur_r--); | |
queries[i].ans = tot; | |
} | |
sort(queries+1, queries+1+q, [](Query a, Query b)->bool { | |
return a.idx < b.idx; | |
}); | |
} | |
int main() { | |
cin >> n; | |
block = sqrt(n); | |
for (int i = 1; i <= n; i++) { | |
cin >> a[i]; | |
} | |
cin >> q; | |
for (int i = 1; i <= q; i++) { | |
cin >> queries[i].l >> queries[i].r; | |
queries[i].bl = queries[i].l/block; | |
queries[i].idx = i; | |
} | |
mo(); | |
for (int i = 1; i <= q; i++) { | |
cout << queries[i].ans << '\n'; | |
} | |
return 0; | |
} |
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