152 lines
3.7 KiB
C++
152 lines
3.7 KiB
C++
/*
|
|
This file is part of Telegram Desktop,
|
|
the official desktop application for the Telegram messaging service.
|
|
|
|
For license and copyright information please follow this link:
|
|
https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
|
|
*/
|
|
#include "statistics/segment_tree.h"
|
|
|
|
namespace Statistic {
|
|
namespace {
|
|
|
|
constexpr auto kMinArraySize = size_t(30);
|
|
|
|
} // namespace
|
|
|
|
SegmentTree::SegmentTree(std::vector<int> array)
|
|
: _array(std::move(array)) {
|
|
if (_array.size() < kMinArraySize) {
|
|
return;
|
|
}
|
|
|
|
// The max size of this array is about 2 * 2 ^ log2(n) + 1.
|
|
const auto size = 2 * std::pow(
|
|
2.,
|
|
std::floor((std::log(_array.size()) / std::log(2.)) + 1));
|
|
_heap.resize(int(size));
|
|
build(1, 0, _array.size());
|
|
}
|
|
|
|
void SegmentTree::build(int v, int from, int size) {
|
|
_heap[v].from = from;
|
|
_heap[v].to = (from + size - 1);
|
|
|
|
if (size == 1) {
|
|
_heap[v].sum = _array[from];
|
|
_heap[v].max = _array[from];
|
|
_heap[v].min = _array[from];
|
|
} else {
|
|
// Build children.
|
|
build(2 * v, from, size / 2);
|
|
build(2 * v + 1, from + size / 2, size - size / 2);
|
|
|
|
_heap[v].sum = _heap[2 * v].sum + _heap[2 * v + 1].sum;
|
|
// max = max of the children.
|
|
_heap[v].max = std::max(_heap[2 * v].max, _heap[2 * v + 1].max);
|
|
_heap[v].min = std::min(_heap[2 * v].min, _heap[2 * v + 1].min);
|
|
}
|
|
}
|
|
|
|
int SegmentTree::rMaxQ(int from, int to) {
|
|
if (_array.size() < kMinArraySize) {
|
|
auto max = 0;
|
|
from = std::max(from, 0);
|
|
to = std::min(to, int(_array.size() - 1));
|
|
for (auto i = from; i <= to; i++) {
|
|
max = std::max(max, _array[i]);
|
|
}
|
|
return max;
|
|
}
|
|
return rMaxQ(1, from, to);
|
|
}
|
|
|
|
int SegmentTree::rMaxQ(int v, int from, int to) {
|
|
const auto &n = _heap[v];
|
|
// If you did a range update that contained this node,
|
|
// you can infer the Min value without going down the tree.
|
|
if (n.pendingVal && contains(n.from, n.to, from, to)) {
|
|
return n.pendingVal.value;
|
|
}
|
|
|
|
if (contains(from, to, n.from, n.to)) {
|
|
return _heap[v].max;
|
|
}
|
|
|
|
if (intersects(from, to, n.from, n.to)) {
|
|
propagate(v);
|
|
const auto leftMin = rMaxQ(2 * v, from, to);
|
|
const auto rightMin = rMaxQ(2 * v + 1, from, to);
|
|
|
|
return std::max(leftMin, rightMin);
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
int SegmentTree::rMinQ(int from, int to) {
|
|
if (_array.size() < kMinArraySize) {
|
|
auto min = std::numeric_limits<int>::max();
|
|
from = std::max(from, 0);
|
|
to = std::min(to, int(_array.size() - 1));
|
|
for (auto i = from; i <= to; i++) {
|
|
min = std::min(min, _array[i]);
|
|
}
|
|
return min;
|
|
}
|
|
return rMinQ(1, from, to);
|
|
}
|
|
|
|
int SegmentTree::rMinQ(int v, int from, int to) {
|
|
const auto &n = _heap[v];
|
|
// If you did a range update that contained this node,
|
|
// you can infer the Min value without going down the tree.
|
|
if (n.pendingVal && contains(n.from, n.to, from, to)) {
|
|
return n.pendingVal.value;
|
|
}
|
|
|
|
if (contains(from, to, n.from, n.to)) {
|
|
return _heap[v].min;
|
|
}
|
|
|
|
if (intersects(from, to, n.from, n.to)) {
|
|
propagate(v);
|
|
const auto leftMin = rMinQ(2 * v, from, to);
|
|
const auto rightMin = rMinQ(2 * v + 1, from, to);
|
|
|
|
return std::min(leftMin, rightMin);
|
|
}
|
|
|
|
return std::numeric_limits<int>::max();
|
|
}
|
|
|
|
void SegmentTree::propagate(int v) {
|
|
auto &n = _heap[v];
|
|
|
|
if (n.pendingVal) {
|
|
const auto value = n.pendingVal.value;
|
|
n.pendingVal = {};
|
|
change(_heap[2 * v], value);
|
|
change(_heap[2 * v + 1], value);
|
|
}
|
|
}
|
|
|
|
void SegmentTree::change(SegmentTree::Node &n, int value) {
|
|
n.pendingVal = { value, true };
|
|
n.sum = n.size() * value;
|
|
n.max = value;
|
|
n.min = value;
|
|
_array[n.from] = value;
|
|
}
|
|
|
|
bool SegmentTree::contains(int from1, int to1, int from2, int to2) const {
|
|
return (from2 >= from1) && (to2 <= to1);
|
|
}
|
|
|
|
bool SegmentTree::intersects(int from1, int to1, int from2, int to2) const {
|
|
return ((from1 <= from2) && (to1 >= from2)) // (.[..)..] or (.[...]..)
|
|
|| ((from1 >= from2) && (from1 <= to2)); // [.(..]..) or [..(..)..
|
|
}
|
|
|
|
} // namespace Statistic
|