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P3834 【模板】可持久化线段树 2

Browse Source 
https://www.luogu.com.cn/record/91986713
This commit is contained in:
Baoshuo Ren 2022-10-29 09:26:29 +08:00
parent cf1446b12c
commit 7bdcaf5f2c
Signed by: baoshuo
GPG Key ID: 00CB9680AB29F51A
1 changed files with 52 additions and 53 deletions
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105
Luogu/P3834/P3834.cpp
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@ -4,88 +4,87 @@
using std::cin;
using std::cout;
using std::endl;
const char endl = '\n';
const int N = 200005;
const int N = 2e5 + 5;
int n, m, l, r, k, a[N];
std::vector<int> nums;
// Helpers
int find(int);
// Segment Tree
int n, m, a[N];
int cnt, root[N];
int build(int, int);
int insert(int, int, int, int);
int query(int, int, int, int, int);
int main() {
cin >> n >> m;
for (int i = 1; i <= n; i++) {
cin >> a[i];
nums.push_back(a[i]);
}
std::sort(nums.begin(), nums.end());
nums.erase(std::unique(nums.begin(), nums.end()), nums.end());
root[0] = build(0, nums.size() - 1);
for (int i = 1; i <= n; i++) {
root[i] = insert(root[i - 1], 0, nums.size() - 1, find(a[i]));
}
while (m--) {
cin >> l >> r >> k;
cout << nums[query(root[r], root[l - 1], 0, nums.size() - 1, k)] << endl;
}
return 0;
}
// === Helpers ===
inline int find(int x) {
return std::lower_bound(nums.begin(), nums.end(), x) - nums.begin();
}
// === Segment Tree ===
std::vector<int> nums;
struct node {
int l, r, c;
node()
: l(0),
r(0),
c(0) {}
} tr[N << 5];
int build(int l, int r) {
int p = ++cnt;
if (l == r) return p;
int mid = l + r >> 1;
tr[p].l = build(l, mid);
tr[p].r = build(mid + 1, r);
return p;
}
int insert(int p, int l, int r, int x) {
int q = ++cnt;
tr[q] = tr[p];
if (l == r) {
tr[q].c++;
return q;
}
int mid = l + r >> 1;
if (x <= mid) {
tr[q].l = insert(tr[p].l, l, mid, x);
} else {
tr[q].r = insert(tr[p].r, mid + 1, r, x);
}
if (x <= mid) tr[q].l = insert(tr[q].l, l, mid, x);
else tr[q].r = insert(tr[q].r, mid + 1, r, x);
tr[q].c = tr[tr[q].l].c + tr[tr[q].r].c;
return q;
}
int query(int q, int p, int l, int r, int k) {
int query(int p, int q, int l, int r, int x) {
if (l == r) return l;
int c = tr[tr[q].l].c - tr[tr[p].l].c;
int c = tr[tr[p].l].c - tr[tr[q].l].c;
int mid = l + r >> 1;
if (k <= c) return query(tr[q].l, tr[p].l, l, mid, k);
return query(tr[q].r, tr[p].r, mid + 1, r, k - c);
if (x <= c) return query(tr[p].l, tr[q].l, l, mid, x);
return query(tr[p].r, tr[q].r, mid + 1, r, x - c);
}
int main() {
std::ios::sync_with_stdio(false);
cin.tie(nullptr);
cin >> n >> m;
for (int i = 1; i <= n; i++) {
cin >> a[i];
nums.emplace_back(a[i]);
}
std::sort(nums.begin(), nums.end());
nums.erase(std::unique(nums.begin(), nums.end()), nums.end());
root[0] = build(0, nums.size() - 1);
for (int i = 1; i <= n; i++) {
root[i] = insert(root[i - 1], 0, nums.size() - 1, std::lower_bound(nums.begin(), nums.end(), a[i]) - nums.begin());
}
while (m--) {
int l, r, k;
cin >> l >> r >> k;
cout << nums.at(query(root[r], root[l - 1], 0, nums.size() - 1, k)) << endl;
}
return 0;
}