Added Leetcode Solution 700: #1412

dsa-solutions/lc-solutions/0700-0799/0700-search-in-a-binary-search-tree.md

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+---
+id: search-in-a-binary-search-tree
+title:   Search in a Binary Search Tree
+sidebar_label: 700. Search in a Binary Search Tree
+
+tags:
+- Binary Tree
+- BST
+- Search
+
+description: "This is a solution to the Search in a Binary Search Tree problem on LeetCode."
+---
+
+## Problem Description
+You are given the `root` of a binary search tree (BST) and an integer `val`.
+Find the node in the BST that the node's value equals `val` and return the subtree rooted with that node. If such a node does not exist, return `null`.
+### Examples
+
+**Example 1:** 
+
+![Example1](image.png)
+```
+Input: root = [4,2,7,1,3], val = 2
+Output: [2,1,3]
+```
+
+**Example 2:**
+
+![Example2](image-1.png)
+```
+Input: root = [4,2,7,1,3], val = 5
+Output: []
+
+```
+
+
+### Constraints
+- The number of nodes in the tree is in the range `[1, 5000]`.
+- `1 <= Node.val <= 10^7`
+- `root` is a binary search tree.
+- `1 <= val <= 10^7`
+
+
+
+## Solution for Search in a Binary Search Tree
+### Approach 
+#### Brute Force 
+- **Traverse the Tree**: Perform a level-order or in-order traversal of the tree.
+- **Compare Values**: At each node, compare its value with the given value `val`.
+- **Return Subtree**: If the node’s value equals `val`, return the subtree rooted at that node.
+- **Return Null**: If the traversal completes without finding the node, return `null`.
+
+**Implementation:**
+```python
+class TreeNode:
+    def __init__(self, val=0, left=None, right=None):
+        self.val = val
+        self.left = left
+        self.right = right
+
+def findNode(root, val):
+    if root is None:
+        return None
+
+    queue = [root]
+    while queue:
+        node = queue.pop(0)
+        if node.val == val:
+            return node
+        if node.left:
+            queue.append(node.left)
+        if node.right:
+            queue.append(node.right)
+
+    return None
+
+# Example usage
+root = TreeNode(4, TreeNode(2, TreeNode(1), TreeNode(3)), TreeNode(7))
+val = 2
+subtree = findNode(root, val)
+print(subtree.val if subtree else "Node not found")
+```
+
+**Complexity:**
+- Time Complexity: `O(n)` - We might have to visit every node in the tree.
+- Space Complexity: `O(n)` - In the worst case, the queue can hold all nodes in the tree (for level-order traversal).
+
+**Corner Cases:**
+- Empty tree: Should return `null`.
+- Value not found: Should return `null`.
+
+#### Optimized Approach 
+- **Leverage BST Properties**: Use the properties of the BST (left subtree contains nodes with values less than the root, and the right subtree contains nodes with values greater than the root).
+- **Binary Search**: Traverse the tree using a binary search-like approach:
+    - If `val` is less than the current node’s value, move to the left child.
+    - If `val` is greater than the current node’s value, move to the right child.
+    - If `val` equals the current node’s value, return the current node.
+- **Return Null**: If a leaf node is reached without finding the value, return `null`.
+
+**Implementation:**
+
+```python
+class TreeNode:
+    def __init__(self, val=0, left=None, right=None):
+        self.val = val
+        self.left = left
+        self.right = right
+
+def findNode(root, val):
+    current = root
+    while current:
+        if current.val == val:
+            return current
+        elif val < current.val:
+            current = current.left
+        else:
+            current = current.right
+    return None
+
+# Example usage
+root = TreeNode(4, TreeNode(2, TreeNode(1), TreeNode(3)), TreeNode(7))
+val = 2
+subtree = findNode(root, val)
+print(subtree.val if subtree else "Node not found")
+```
+
+**Complexity:**
+- Time Complexity: `O(h)`- `h` is the height of the tree. In the worst case, it can be O(n) for a skewed tree, but in a balanced tree, it is O(log n).
+- Space Complexity: `O(1)`- We are not using any extra space except for the input and output.
+
+**Corner Cases:**
+- Empty tree: Should return `null`.
+- Value not found: Should return `null`.
+- Single node tree: If the single node does not match `val`, should return `null`.
+
+
+  ## Code in Different Languages
+
+ <Tabs>
+
+  <TabItem value="JavaScript" label="JavaScript">
+  <SolutionAuthor name="@vansh-codes" />
+
+   ```javascript
+    var searchBST = function(root, val) {
+        if (root === null) {
+            return null;
+        } else {
+            if (root.val === val) {
+                return root;
+            } else if (root.val < val) {
+                return searchBST(root.right, val);
+            } else {
+                return searchBST(root.left, val);
+            }
+        }
+    };
+    ```
+
+  </TabItem>
+
+  <TabItem value="TypeScript" label="TypeScript">
+  <SolutionAuthor name="@vansh-codes" /> 
+
+   ```typescript
+    function searchBST(root: TreeNode | null, val: number): TreeNode | null {
+        if (root === null) {
+            return null;
+        } else {
+            if (root.val === val) {
+                return root;
+            } else if (root.val < val) {
+                return searchBST(root.right, val);
+            } else {
+                return searchBST(root.left, val);
+            }
+        }
+    }
+    ```
+
+  </TabItem>
+
+  <TabItem value="Python" label="Python">
+  <SolutionAuthor name="@vansh-codes" />
+
+   ```python
+
+    class Solution(object):
+    def searchBST(self, root, val):
+        if root is None:
+            return None
+        else:
+            if root.val == val:
+                return root
+            elif root.val < val:
+                return self.searchBST(root.right, val)
+            else:
+                return self.searchBST(root.left, val)
+    ```
+
+  </TabItem>
+
+  <TabItem value="Java" label="Java">
+  <SolutionAuthor name="@vansh-codes" />
+
+   ```java
+   import java.util.Arrays;
+
+    class Solution {
+        public TreeNode searchBST(TreeNode root, int val) {
+            if (root == null) {
+                return null;
+            } else {
+                if (root.val == val) {
+                    return root;
+                } else if (root.val < val) {
+                    return searchBST(root.right, val);
+                } else {
+                    return searchBST(root.left, val);
+                }
+            }
+        }
+    }
+    ```
+
+  </TabItem>
+
+ <TabItem value="C++" label="C++">
+ <SolutionAuthor name="@vansh-codes" />
+
+   ```cpp
+   class Solution {
+    public:
+        TreeNode* searchBST(TreeNode* root, int val) {
+            if(root==NULL){
+                return NULL;
+            }
+            else{
+                if(root->val == val){
+                        return root;
+                }else if(root->val < val){
+                        return searchBST(root->right,val);
+                }else{
+                        return searchBST(root->left,val);
+                }
+                return NULL;
+            }
+            return NULL;
+        }
+    };
+    ```
+
+ </TabItem>
+ </Tabs>
+
+## References
+
+- **LeetCode Problem**: [Search in a Binary Search Tree](https://leetcode.com/problems/search-in-a-binary-search-tree/description)
+
+- **Solution Link**: [LeetCode Solution](https://leetcode.com/problems/search-in-a-binary-search-tree/solutions)