add khushal87 codes

BST/find_pair_sum_in_bst.cpp

@@ -0,0 +1,32 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+struct Node
+{
+ int data;
+ Node *left;
+ Node *right;
+};
+
+bool findPairUtil(Node *root, int target, set<int> &st)
+{
+ if (root == nullptr)
+ return false;
+ if (findPairUtil(root->left, target, st))
+ {
+ return true;
+ }
+ if (st.find(target - root->data) != st.end())
+ {
+ cout << root->data << " " << target - root->data << endl;
+ return true;
+ }
+ else
+ {
+ st.insert(root->data);
+ }
+ if (findPairUtil(root->right, target, st))
+ {
+ return true;
+ }
+}

BST/floor_ceil.cpp

@@ -0,0 +1,35 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+struct Node
+{
+ int data;
+ Node *left;
+ Node *right;
+};
+
+pair<int, int> floorCeil(Node *root, int key)
+{
+ if (root == nullptr)
+ return {};
+ else
+ {
+ pair<int, int> p;
+ if (root->data == key)
+ {
+ p.first = root->data;
+ p.second = root->data;
+ }
+ else if (root->data < key)
+ {
+ p.first = root->data;
+ root = root->right;
+ }
+ else
+ {
+ p.second = root->data;
+ root = root->left;
+ }
+ return p;
+ }
+}

BST/inorder_predecessor_and_successor.cpp

@@ -0,0 +1,51 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+struct Node
+{
+ int data;
+ Node *left;
+ Node *right;
+};
+
+pair<Node *, Node *> preSuc(Node *root, int data)
+{
+ if (root == nullptr)
+ return {};
+ else
+ {
+ pair<Node *, Node *> p;
+ if (root->data == data)
+ {
+ if (root->left)
+ {
+ Node *temp = root->left;
+ while (temp->right)
+ {
+ temp = temp->right;
+ }
+ p.first = temp;
+ }
+ if (root->right)
+ {
+ Node *temp = root->right;
+ while (temp->left)
+ {
+ temp = temp->left;
+ }
+ p.second = temp;
+ }
+ }
+ else if (root->data > data)
+ {
+ p.second = root;
+ preSuc(root->left, data);
+ }
+ else
+ {
+ p.first = root;
+ preSuc(root->right, data);
+ }
+ return p;
+ }
+}

BST/number_of_nodes_in_a_range.cpp

@@ -0,0 +1,23 @@
+
+class Tree
+{
+public:
+ int val;
+ Tree *left;
+ Tree *right;
+};
+
+int answer(Tree *root, int lo, int hi)
+{
+ if (root == nullptr)
+ return 0;
+ else
+ {
+ if (root->val >= lo && root->val <= hi)
+ return 1 + answer(root->left, lo, hi) + answer(root->right, lo, hi);
+ else if (root->val < lo)
+ return answer(root->right, lo, hi);
+ else
+ return answer(root->left, lo, hi);
+ }
+}

Graph/undirected_graph_has_cycle_or_not.cpp

@@ -12,13 +12,10 @@ bool dfs(vector<vector<int>> &adj, vector<bool> &vis, int i, int parent)
  {
  return true;
  }
- else
- {
- if (j != parent)
- {
- return true;
- }
- }
+ }
+ else if (j != parent)
+ {
+ return true;
  }
  }
  return false;

Heap/heap_sort.cpp

@@ -44,6 +44,7 @@ int main()
  {
  cin >> arr[i];
  }
+ heapSort(arr, n);
  reverse(arr, arr + n);
  for (int i = 0; i < n; i++)
  {

LinkedList/remove_duplicate_In_unsorted_linked_list.cpp

@@ -0,0 +1,36 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+struct Node
+{
+ int data;
+ struct Node *next;
+ Node(int x)
+ {
+ data = x;
+ next = NULL;
+ }
+};
+
+Node *removeDuplicates(Node *head)
+{
+ // your code goes here
+ unordered_set<int> st;
+ Node *curr = head;
+ Node *prev = nullptr;
+ while (curr != nullptr)
+ {
+ if (st.find(curr->data) != st.end())
+ {
+ prev->next = curr->next;
+ delete curr;
+ }
+ else
+ {
+ st.insert(curr->data);
+ prev = curr;
+ }
+ curr = prev->next;
+ }
+ return head;
+}

LinkedList/remove_duplicate_in_sorted_linked_list.cpp

@@ -0,0 +1,37 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+struct Node
+{
+ int data;
+ struct Node *next;
+ Node(int x)
+ {
+ data = x;
+ next = NULL;
+ }
+};
+
+//Function to remove duplicates from sorted linked list.
+Node *removeDuplicates(Node *head)
+{
+ // your code goes here
+ if (head == nullptr)
+ return nullptr;
+ Node *curr = head;
+ Node *next;
+ while (curr->next != nullptr)
+ {
+ if (curr->data == curr->next->data)
+ {
+ next = curr->next->next;
+ free(curr->next);
+ curr->next = next;
+ }
+ else
+ {
+ curr = curr->next;
+ }
+ }
+ return head;
+}