Create DeleteNodeinaBST.java

Leetcode/DeleteNodeinaBST.java

@@ -0,0 +1,70 @@
+/**
+450. Delete Node in a BST
+Solved
+Medium
+Topics
+Companies
+Given a root node reference of a BST and a key, delete the node with the given key in the BST. Return the root node reference (possibly updated) of the BST.
+
+Basically, the deletion can be divided into two stages:
+
+Search for a node to remove.
+If the node is found, delete the node.
+ **/
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+
+class Solution {
+    public TreeNode deleteNode(TreeNode root, int key) {
+        //search
+        if(root == null ) {
+            return null;
+        }
+        if(root.val<key){
+            root.right = deleteNode(root.right,key);
+        }
+        else if(root.val>key) {
+            root.left = deleteNode(root.left,key);
+        }
+        else{
+            //case 1: leaf node
+            if(root.left == null && root.right == null ) {
+                return null;
+            }
+            //case 2 : one child
+            if(root.left ==  null){
+                return root.right;
+            }
+            else if(root.right ==  null ) {
+                return root.left;
+            }
+            //case 3 : two children
+            TreeNode IS = findInOrderSuccessor(root.right);
+            root.val = IS.val;
+
+
+            root.right = deleteNode(root.right,IS.val);
+        }
+        return root;
+
+    }
+    private TreeNode findInOrderSuccessor(TreeNode root){
+        while(root.left != null){
+            root = root.left;
+        }
+        return root;
+    }
+}