450. Delete Node in a BST

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    TreeNode findMin(TreeNode root)
    {
        while(root.left!=null)
            root=root.left;
        return root;
    }
    public TreeNode deleteNode(TreeNode root, int key) {
        if(null==root)return null;
        if(key<root.val)
            root.left=deleteNode(root.left,key);
        else if(key>root.val)
            root.right=deleteNode(root.right,key);
        else
        {
        if(null==root.left)
            return root.right;
        else if(null==root.right)
            return root.left;
        
        TreeNode min=findMin(root.right);
        root.val=min.val;
        root.right=deleteNode(root.right,min.val);
        }
        return root;
    }
}