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MSedra 2021-01-27 23:27:31 +02:00
parent de595b0c19
commit f3ba7fa90e
1 changed files with 14 additions and 16 deletions
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30
range_queries/persistent_segment_tree_with_lazy_propagation.cpp
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@ -47,16 +47,19 @@ private:
curr->prop = 0; curr->prop = 0;
} }
void construct(int i, int j, std::shared_ptr<Node> &curr) { std::shared_ptr<Node> construct(int i, int j) {
curr = std::make_shared<Node>(Node()); auto newNode = std::make_shared<Node>(Node());
if (i == j) { if (i == j) {
curr->val = vec[i]; newNode->val = vec[i];
} else { } else {
int mid = i + (j - i) / 2; int mid = i + (j - i) / 2;
construct(i, mid, curr->left); auto leftt = construct(i, mid);
construct(mid + 1, j, curr->right); auto right = construct(mid + 1, j);
curr->val = curr->left->val + curr->right->val; newNode->val = leftt->val + right->val;
newNode->left = leftt;
newNode->right = right;
} }
return newNode;
} }
std::shared_ptr<Node> update(int i, int j, int l, int r, int value, std::shared_ptr<Node> const &curr) { std::shared_ptr<Node> update(int i, int j, int l, int r, int value, std::shared_ptr<Node> const &curr) {
@ -97,34 +100,29 @@ public:
n = 0; n = 0;
} }
void construct( void construct(const std::vector<int> &vec) // the segment tree will be built from the values in "vec", "vec" is 0 indexed
const std::vector<int> &vec) // the segment tree will be built from the values in "vec", "vec" is 0 indexed
{ {
if (vec.empty()) { if (vec.empty()) {
return; return;
} }
n = vec.size(); n = vec.size();
this->vec = vec; this->vec = vec;
std::shared_ptr<Node> root = nullptr; auto root = construct(0, n - 1);
construct(0, n - 1, root);
ptrs.push_back(root); ptrs.push_back(root);
} }
void update(int l, int r, void update(int l, int r, int value) // all elements from index "l" to index "r" would by updated by "value", "l" and "r" are 0 indexed
int value) // all elements from index "l" to index "r" would by updated by "value", "l" and "r" are 0 indexed
{ {
ptrs.push_back(update(0, n - 1, l, r, value, ptrs.push_back(update(0, n - 1, l, r, value,
ptrs[ptrs.size() - 1])); // saving the root pointer to the new segment tree ptrs[ptrs.size() - 1])); // saving the root pointer to the new segment tree
} }
int64_t query(int l, int r, int64_t query(int l, int r, int version) // querying the range from "l" to "r" in a segment tree after "version" updates, "l" and "r" are 0 indexed
int version) // querying the range from "l" to "r" in a segment tree after "version" updates, "l" and "r" are 0 indexed
{ {
return query(0, n - 1, l, r, ptrs[version]); return query(0, n - 1, l, r, ptrs[version]);
} }
int int size() // returns the number of segment trees (versions) , the number of updates done so far = returned value - 1 ,because one of the trees is the original segment tree
size() // returns the number of segment trees (versions) , the number of updates done so far = returned value - 1 ,because one of the trees is the original segment tree
{ {
return ptrs.size(); return ptrs.size();
} }