OpenSoure_Repos/TheAlgorithms-C-Plus-Plus
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MSedra 2021-01-27 19:44:14 +02:00
parent 558b74f1dd
commit b999e1848f
1 changed files with 23 additions and 24 deletions
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47
range_queries/persistent_segment_tree_with_lazy_propagation.cpp
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@ -5,8 +5,7 @@
// query -> range sum // query -> range sum
class perSegTree { class perSegTree {
private: private:
class Node { struct Node {
public:
Node *left; Node *left;
Node *right; Node *right;
int64_t val, prop; int64_t val, prop;
@ -20,8 +19,10 @@ private:
int n; // number of elements in the segment tree int n; // number of elements in the segment tree
std::vector<Node *> ptrs; // ptrs[i] holds a root pointer to the segment tree after the ith update std::vector<Node *> ptrs; // ptrs[i] holds a root pointer to the segment tree after the ith update
std::vector<int> vec;
Node *newKid(Node *curr) { Node *newKid(Node *curr) {
Node *newNode = new Node(); Node *newNode = new Node;
*newNode = *curr; *newNode = *curr;
return newNode; return newNode;
} }
@ -41,14 +42,14 @@ private:
curr->prop = 0; curr->prop = 0;
} }
void construct(int i, int j, std::vector<int> &vec, Node *&curr) { void construct(int i, int j, Node *&curr) {
curr = new Node(); curr = new Node;
if (i == j) { if (i == j) {
curr->val = vec[i]; curr->val = vec[i];
} else { } else {
int mid = i + (j - i) / 2; int mid = i + (j - i) / 2;
construct(i, mid, vec, curr->left); construct(i, mid, curr->left);
construct(mid + 1, j, vec, curr->right); construct(mid + 1, j, curr->right);
curr->val = curr->left->val + curr->right->val; curr->val = curr->left->val + curr->right->val;
} }
} }
@ -65,7 +66,7 @@ private:
if (i > r || j < l) { if (i > r || j < l) {
return curr; return curr;
} }
Node *newNode = new Node(); Node *newNode = new Node;
int mid = i + (j - i) / 2; int mid = i + (j - i) / 2;
newNode->left = update(i, mid, l, r, value, curr->left); newNode->left = update(i, mid, l, r, value, curr->left);
newNode->right = update(mid + 1, j, l, r, value, curr->right); newNode->right = update(mid + 1, j, l, r, value, curr->right);
@ -86,7 +87,7 @@ private:
return query(i, mid, l, r, curr->left) + query(mid + 1, j, l, r, curr->right); return query(i, mid, l, r, curr->left) + query(mid + 1, j, l, r, curr->right);
} }
void clear(Node *&curr, int version) { /*void clear(Node *&curr, int version) {
if (!curr || curr->version != version) { if (!curr || curr->version != version) {
return; return;
} }
@ -94,48 +95,47 @@ private:
clear(curr->right, version); clear(curr->right, version);
delete curr; delete curr;
} }
*/ // for deallocation , version is passed to delete the current node iff its version = passed version
// that is, this node was created when the segment tree, whose version = this node's version, was created
// this is done to delete the segment trees top down version by version
public: public:
perSegTree() { perSegTree() {
n = 0; n = 0;
} }
void construct(std::vector<int> &vec) // the segment tree will be built from the values in "vec", "vec" is 0 indexed void construct(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;
Node *root = nullptr; Node *root = nullptr;
construct(0, n - 1, vec, root); 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]);
} }
void clear() { /*void clear() {
for (int i = (int) ptrs.size() - 1; i >= 0; --i) { for (int i = static_cast<int>(ptrs.size()) - 1; i >= 0; --i) {
clear(ptrs[i], clear(ptrs[i],i); // every segment tree clears its nodes (nodes that were created when this segment tree was created)
i); // every segment tree clears its nodes (nodes that were created when this segment tree was created)
} }
while (!ptrs.empty()) { while (!ptrs.empty()) {
ptrs.pop_back(); ptrs.pop_back();
} }
} }*/
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();
} }
@ -178,5 +178,4 @@ int main() {
std::cout << "Number of segment trees (versions) now = " << tree.size() << '\n'; std::cout << "Number of segment trees (versions) now = " << tree.size() << '\n';
std::cout << "Querying range sum on version 0 from index 3 to 5 = 11-2+7 = " << tree.query(3, 5, 0) << '\n'; std::cout << "Querying range sum on version 0 from index 3 to 5 = 11-2+7 = " << tree.query(3, 5, 0) << '\n';
std::cout << "Querying range sum on version 1 from index 3 to 5 = 4-9+0 = " << tree.query(3, 5, 1) << '\n'; std::cout << "Querying range sum on version 1 from index 3 to 5 = 4-9+0 = " << tree.query(3, 5, 1) << '\n';
tree.clear();
} }