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segment_tree.cpp
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216 lines (169 loc) · 4.34 KB
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#include <iostream>
#include <vector>
using namespace std;
class SegmentTree
{
public:
SegmentTree(vector<int>& nums)
{
m_n = nums.size();
m_tree.resize(4*m_n, 0);
m_lazy.resize(4*m_n, 0);
build_tree(nums, 0, 0, m_n - 1);
}
void update(int pos, int val)
{
update_tree(0, 0, m_n - 1, pos, val);
}
void update_range(int i, int j, int val)
{
update_lazy_tree(0, 0, m_n - 1, i, j, val);
}
int query(int i, int j)
{
return query_tree(0, 0, m_n - 1, i, j);
}
int query_lazy(int i, int j)
{
return query_lazy_tree(0, 0, m_n - 1, i, j);
}
auto traverse() -> vector<int>
{
vector<int> res;
traverse_tree(res, 0, 0, m_n - 1);
return res;
}
private:
void build_tree(vector<int>& arr, int ti, int lo, int hi)
{
if (lo == hi)
{
m_tree[ti] = arr[lo];
return;
}
auto mid = lo + (hi - lo) / 2;
build_tree(arr, 2*ti + 1, lo, mid);
build_tree(arr, 2*ti + 2, mid+1, hi);
m_tree[ti] = m_tree[2*ti + 1] + m_tree[2*ti + 2];
}
void traverse_tree(vector<int>& res, int ti, int lo, int hi)
{
if (lo == hi) {
res.push_back(m_tree[ti]);
return;
}
auto mid = lo + (hi - lo) / 2;
traverse_tree(res, 2*ti + 1, lo, mid);
traverse_tree(res, 2*ti + 2, mid + 1, hi);
}
int query_tree(int ti, int lo, int hi, int i, int j)
{
if (i > hi or j < lo)
return 0;
if (i == lo and j == hi)
return m_tree[ti];
auto mid = lo + (hi - lo) / 2;
if (i > mid)
return query_tree(2*ti + 2, mid + 1, hi, i, j);
else if (j <= mid)
return query_tree(2*ti + 1, lo, mid, i, j);
auto lq = query_tree(ti*2 + 1, lo, mid, i, j);
auto rq = query_tree(ti*2 + 2, mid + 1, hi, i, j);
return lq + rq;
}
int query_lazy_tree(int ti, int lo, int hi, int i, int j)
{
if (i > hi or j < lo)
return 0;
if (m_lazy[ti] != 0)
{
m_tree[ti] += (hi - lo + 1) * m_lazy[ti]; // normalize current node by removing laziness
if (lo != hi)
{
m_lazy[2*ti + 1] += m_lazy[ti]; // update lazy[] for children nodes
m_lazy[2*ti + 2] += m_lazy[ti];
}
m_lazy[ti] = 0;
}
if (i <= lo and j >= hi)
return m_tree[ti];
auto mid = lo + (hi - lo) / 2;
if (i > mid)
return query_lazy_tree(2*ti + 2, mid + 1, hi, i, j);
else if (j <= mid)
return query_lazy_tree(2*ti + 1, lo, mid, i, j);
auto lq = query_lazy_tree(2*ti + 1, lo, mid + i, i, mid);
auto rq = query_lazy_tree(2*ti + 2, mid + 1, hi, mid + 1, j);
return lq + rq;
}
void update_tree(int ti, int lo, int hi, int ai, int val)
{
if (lo == hi)
{
m_tree[ti] = val;
return;
}
auto mid = lo + (hi - lo) / 2;
if (ai > mid)
update_tree(2*ti + 2, mid + 1, hi, ai, val);
else
update_tree(2*ti + 1, lo, mid, ai, val);
m_tree[ti] = m_tree[2*ti + 1] + m_tree[2*ti + 2];
}
void update_lazy_tree(int ti, int lo, int hi, int i, int j, int val)
{
if (m_lazy[ti] != 0)
{
m_tree[ti] += (hi - lo + 1) * m_lazy[ti]; // normalize current node by removing laziness
if (lo != hi)
{
m_lazy[2*ti + 1] += m_lazy[ti]; // update lazy[] for children nodes
m_lazy[2*ti + 2] += m_lazy[ti];
}
m_lazy[ti] = 0;
}
if (lo > hi or lo > j or hi < i)
return;
if (i <= lo and hi <= j)
{
m_tree[ti] += (hi - lo + 1) * val;
if (lo != hi)
{
m_lazy[2*ti + 1] += val;
m_lazy[2*ti + 2] += val;
}
return;
}
auto mid = lo + (hi - lo) / 2;
update_lazy_tree(2*ti + 1, lo, mid, i, j, val);
update_lazy_tree(2*ti + 2, mid+1, hi, i, j, val);
// merge updates
m_tree[ti] = m_tree[2*ti + 1] + m_tree[2*ti + 2];
}
private:
vector<int> m_tree, m_lazy;
int m_n;
};
void p(vector<int>&& nums)
{
for (auto i: nums) cout << i << " ";
cout << endl;
cout.flush();
}
int main(int argc, char *argv[])
{
vector<int> arr = { 1, 10, 3, 6, 5, 6, 4 };
SegmentTree sg(arr);
cout << sg.query(0, 6) << " : ";
p(sg.traverse());
sg.update(6, 2);
cout << sg.query(0, 6) << " : ";
p(sg.traverse());
sg.update_range(1, 3, 2);
cout << sg.query_lazy(0, 6) << " : ";
p(sg.traverse());
cout << sg.query_lazy(2, 2) << endl;
cout << sg.query_lazy(3, 3) << endl;
p(sg.traverse());
return 0;
}