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segment_tree
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segment_tree
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#include <bits/stdc++.h>
using namespace std;
class SegmentTree {
vector<int> tree;
int size;
public:
SegmentTree(vector<int>& array) {
size = array.size();
tree.resize(4 * size);
buildTree(array, 0, 0, size - 1);
}
private:
void buildTree(vector<int>& array, int treeIndex, int left, int right) {
if (left == right) {
tree[treeIndex] = array[left];
return;
}
int mid = left + (right - left) / 2;
buildTree(array, 2 * treeIndex + 1, left, mid);
buildTree(array, 2 * treeIndex + 2, mid + 1, right);
tree[treeIndex] = min(tree[2 * treeIndex + 1], tree[2 * treeIndex + 2]);
}
int query(int treeIndex, int left, int right, int queryLeft, int queryRight) {
if (queryLeft <= left && right <= queryRight)
return tree[treeIndex];
int mid = left + (right - left) / 2;
int minValue = INT_MAX;
if (queryLeft <= mid)
minValue = min(minValue, query(2 * treeIndex + 1, left, mid, queryLeft, queryRight));
if (queryRight > mid)
minValue = min(minValue, query(2 * treeIndex + 2, mid + 1, right, queryLeft, queryRight));
return minValue;
}
public:
int query(int left, int right) {
return query(0, 0, size - 1, left, right);
}
};
int main() {
vector<int> array = {1, 3, 2, 5, 4, 6};
SegmentTree st(array);
cout << st.query(1, 5) << endl; // 2
return 0;
}