Added some solution

codeAbinash · Aug 29, 2023 · e5b76dc · e5b76dc
1 parent ca56be4
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diff --git a/leetcode/problems/cpp/binary-search-tree-iterator.cpp b/leetcode/problems/cpp/binary-search-tree-iterator.cpp
@@ -0,0 +1,42 @@
+// by @codeAbinash
+// Time : O(n)
+// Space : O(n)
+
+#include "stack"
+using namespace std;
+
+struct TreeNode {
+   int val;
+   TreeNode* left;
+   TreeNode* right;
+   TreeNode() : val(0), left(nullptr), right(nullptr) {}
+   TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+   TreeNode(int x, TreeNode* left, TreeNode* right) : val(x), left(left), right(right) {}
+};
+
+class BSTIterator {
+   stack<TreeNode*> st;
+   void partInorder(TreeNode* root) {
+      if (!root) return;
+      while (root) {
+         st.push(root);
+         root = root->left;
+      }
+   }
+
+public:
+   BSTIterator(TreeNode* root) {
+      partInorder(root);
+   }
+
+   int next() {
+      TreeNode* top = st.top();
+      st.pop();
+      if (top->right) partInorder(top->right);
+      return top->val;
+   }
+
+   bool hasNext() {
+      return !st.empty();
+   }
+};
diff --git a/leetcode/problems/cpp/binary-tree-zigzag-level-order-traversal.cpp b/leetcode/problems/cpp/binary-tree-zigzag-level-order-traversal.cpp
@@ -0,0 +1,48 @@
+// by @codeAbinash
+// Time : O(n)
+// Space : O(n)
+
+#include "vector"
+#include "queue"
+#include "algorithm"
+using namespace std;
+
+
+struct TreeNode {
+   int val;
+   TreeNode* left;
+   TreeNode* right;
+   TreeNode() : val(0), left(nullptr), right(nullptr) {}
+   TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+   TreeNode(int x, TreeNode* left, TreeNode* right) : val(x), left(left), right(right) {}
+};
+
+class Solution {
+public:
+   vector<vector<int>> zigzagLevelOrder(TreeNode* root) {
+      vector<vector<int>> ans;
+      queue<TreeNode*> q;
+      bool dir = true;
+
+      if (!root) return ans;
+      q.push(root);
+      vector<int> tmp;
+
+      while (!q.empty()) {
+         int size = q.size();
+         while (size--) {
+            TreeNode* front = q.front();
+            tmp.push_back(front->val);
+            q.pop();
+            if (front->left) q.push(front->left);
+            if (front->right) q.push(front->right);
+         }
+         if (dir = !dir)
+            reverse(tmp.begin(), tmp.end());
+         ans.push_back(tmp);
+         tmp.clear();
+      }
+
+      return ans;
+   }
+};
diff --git a/leetcode/problems/cpp/count-complete-tree-nodes.cpp b/leetcode/problems/cpp/count-complete-tree-nodes.cpp
@@ -0,0 +1,30 @@
+// by @codeAbinash
+// Time : O(log n * log n)
+// Space : O(1)
+
+struct TreeNode {
+   int val;
+   TreeNode* left;
+   TreeNode* right;
+   TreeNode() : val(0), left(nullptr), right(nullptr) {}
+   TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+   TreeNode(int x, TreeNode* left, TreeNode* right) : val(x), left(left), right(right) {}
+};
+
+class Solution {
+public:
+   int countNodes(TreeNode* root) {
+      if (!root) return 0;
+      TreeNode* left = root, * right = root;
+      int height = 0;
+
+      while (right) {
+         left = left->left;
+         right = right->right;
+         height++;
+      }
+
+      if (!left) return (1 << height) - 1;
+      return 1 + countNodes(root->left) + countNodes(root->right);
+   }
+};