From dc4783bc4de09a18f3364b42cf15b67ec8ea69d1 Mon Sep 17 00:00:00 2001 From: Baoshuo Date: Wed, 22 Dec 2021 17:02:07 +0800 Subject: [PATCH] SP3946 MKTHNUM - K-th Number R65565908 --- Luogu/SP3946/SP3946.cpp | 89 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 89 insertions(+) create mode 100644 Luogu/SP3946/SP3946.cpp diff --git a/Luogu/SP3946/SP3946.cpp b/Luogu/SP3946/SP3946.cpp new file mode 100644 index 00000000..747ffaf7 --- /dev/null +++ b/Luogu/SP3946/SP3946.cpp @@ -0,0 +1,89 @@ +#include +#include +#include + +using std::cin; +using std::cout; +using std::endl; + +const int N = 200005; + +int n, m, l, r, k, a[N]; +std::vector nums; + +// Helpers +int find(int); + +// Segment Tree +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 === + +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); + } + 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) { + if (l == r) return l; + int c = tr[tr[q].l].c - tr[tr[p].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); +}