leetcode

Author: ayoubzulfiqar

InvertBinaryTree/invert_binary_tree.dart

@@ -0,0 +1,96 @@
+/*
+
+
+-* Invert Binary Tree *-
+
+Given the root of a binary tree, invert the tree, and return its root.
+
+
+
+Example 1:
+
+
+Input: root = [4,2,7,1,3,6,9]
+Output: [4,7,2,9,6,3,1]
+Example 2:
+
+
+Input: root = [2,1,3]
+Output: [2,3,1]
+Example 3:
+
+Input: root = []
+Output: []
+
+
+Constraints:
+
+The number of nodes in the tree is in the range [0, 100].
+-100 <= Node.val <= 100
+
+*/
+
+// Definition for a binary tree node.
+import 'dart:collection';
+
+class TreeNode {
+  int val;
+  TreeNode? left;
+  TreeNode? right;
+  TreeNode([this.val = 0, this.left, this.right]);
+}
+
+class A {
+  // recursive
+  TreeNode? invertTree(TreeNode? root) {
+    if (root == null) return null;
+    TreeNode? tempRight = root.right;
+    root.right = invertTree(root.left);
+    root.left = invertTree(tempRight);
+    return root;
+  }
+}
+
+class B {
+  // Using Queue
+  TreeNode? invertTree(TreeNode? root) {
+    if (root == null) return null;
+
+    final Queue<TreeNode> stack = Queue();
+    stack.add(root);
+
+    while (stack.isNotEmpty) {
+      final TreeNode node = stack.removeLast();
+      final TreeNode? left = node.left;
+      node.left = node.right;
+      node.right = left;
+
+      if (node.left != null) stack.add(node.left!);
+
+      if (node.right != null) stack.add(node.right!);
+    }
+    return root;
+  }
+}
+
+class C {
+  // Depth First Search
+  TreeNode? invertTree(TreeNode? root) {
+    if (root == null) return null;
+
+    final Queue<TreeNode> queue = Queue();
+    queue.add(root);
+
+    while (queue.isNotEmpty) {
+      final TreeNode node = queue.removeFirst();
+      final TreeNode? left = node.left;
+      node.left = node.right;
+      node.right = left;
+
+      if (node.left != null) queue.add(node.left!);
+
+      if (node.right != null) queue.add(node.right!);
+    }
+    return root;
+  }
+}

InvertBinaryTree/invert_binary_tree.go

@@ -0,0 +1,25 @@
+package main
+
+// Definition for a binary tree node.
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
+func invertTree(root *TreeNode) *TreeNode {
+	stack := []*TreeNode{root}
+
+	for len(stack) != 0 {
+		pop := stack[len(stack)-1]
+		stack = stack[:len(stack)-1]
+
+		if pop != nil {
+			pop.Right, pop.Left = pop.Left, pop.Right
+			stack = append(stack, pop.Right, pop.Left)
+		}
+
+	}
+
+	return root
+}

InvertBinaryTree/invert_binary_tree.md

@@ -0,0 +1,80 @@
+# 🔥 Invert Binary Tree 🔥 || 3 Solutions || Simple Fast and Easy || with Explanation
+
+## Definition for a binary tree node
+
+```dart
+class TreeNode {
+  int val;
+  TreeNode? left;
+  TreeNode? right;
+  TreeNode([this.val = 0, this.left, this.right]);
+}
+```
+
+## Solution - 1 Recursive
+
+```dart
+class Solution {
+  TreeNode? invertTree(TreeNode? root) {
+    if (root == null) return null;
+    TreeNode? tempRight = root.right;
+    root.right = invertTree(root.left);
+    root.left = invertTree(tempRight);
+    return root;
+  }
+}
+```
+
+## Solution - 2 Using Queue as Stack
+
+```dart
+import 'dart:collection';
+
+class Solution {
+  TreeNode? invertTree(TreeNode? root) {
+    if (root == null) return null;
+
+    final Queue<TreeNode> stack = Queue();
+    stack.add(root);
+
+    while (stack.isNotEmpty) {
+      final TreeNode node = stack.removeLast();
+      final TreeNode? left = node.left;
+      node.left = node.right;
+      node.right = left;
+
+      if (node.left != null) stack.add(node.left!);
+
+      if (node.right != null) stack.add(node.right!);
+    }
+    return root;
+  }
+}
+```
+
+## Solution - 3 BFS (Level Order Traversal)
+
+```dart
+import 'dart:collection';
+
+class Solution {
+  TreeNode? invertTree(TreeNode? root) {
+    if (root == null) return null;
+
+    final Queue<TreeNode> queue = Queue();
+    queue.add(root);
+
+    while (queue.isNotEmpty) {
+      final TreeNode node = queue.removeFirst();
+      final TreeNode? left = node.left;
+      node.left = node.right;
+      node.right = left;
+
+      if (node.left != null) queue.add(node.left!);
+
+      if (node.right != null) queue.add(node.right!);
+    }
+    return root;
+  }
+}
+```

README.md

@@ -79,6 +79,7 @@ This repo contain leetcode solution using DART and GO programming language. Most
 - [Contains Duplicate](ContainsDuplicate/contains_duplicate.dart)
 - [Contains Duplicate II](ContainsDuplicate-II/contains_duplicate_II.dart)
 - [Implement Stack using Queues](ImplementStackUsingQueues/implement_stack_using_queues.dart)
+- [Invert Binary Tree](InvertBinaryTree/invert_binary_tree.dart)
 
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