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OI-codes/Luogu/SP3267/SP3267.cpp

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#include <iostream>
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#include <algorithm>
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#include <map>
#include <vector>
using std::cin;
using std::cout;
using std::endl;
const int N = 300005;
int n, q, a[N], pre[N];
std::map<int, int> map;
// Segment Tree
int cnt, root[N];
int build(int, int);
int insert(int, int, int);
int query(int, int);
int main() {
cin >> n;
for (int i = 1; i <= n; i++) {
cin >> a[i];
}
root[0] = build(1, n);
for (int i = 1; i <= n; i++) {
if (!map.count(a[i])) {
root[i] = insert(root[i - 1], i, 1);
} else {
int tmp = insert(root[i - 1], map[a[i]], -1);
root[i] = insert(tmp, i, 1);
}
map[a[i]] = i;
}
cin >> q;
while (q--) {
int l, r;
cin >> l >> r;
cout << query(root[r], l) << endl;
}
return 0;
}
// === Segment Tree ===
struct node {
int l, r, c;
int lid, rid;
node()
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: l(0),
r(0),
c(0),
lid(0),
rid(0) {}
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node(int _l, int _r)
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: l(_l),
r(_r),
c(0),
lid(0),
rid(0) {}
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} tr[N << 7];
inline void pushup(int u) {
tr[u].c = tr[tr[u].lid].c + tr[tr[u].rid].c;
}
int build(int l, int r) {
int p = ++cnt;
tr[p] = node(l, r);
if (l == r) return p;
int mid = l + r >> 1;
tr[p].lid = build(l, mid);
tr[p].rid = build(mid + 1, r);
return p;
}
int insert(int p, int x, int v) {
int q = ++cnt;
tr[q] = tr[p];
if (tr[q].l == tr[q].r) {
tr[q].c += v;
return q;
}
int mid = tr[q].l + tr[q].r >> 1;
if (x <= mid) {
tr[q].lid = insert(tr[p].lid, x, v);
} else {
tr[q].rid = insert(tr[p].rid, x, v);
}
pushup(q);
return q;
}
int query(int u, int x) {
if (tr[u].l == tr[u].r) return tr[u].c;
int mid = tr[u].l + tr[u].r >> 1;
if (x <= mid) return tr[tr[u].rid].c + query(tr[u].lid, x);
return query(tr[u].rid, x);
}