BST delete.java

/**
 * Definition of TreeNode:
 * public class TreeNode {
 *     public int val;
 *     public TreeNode left, right;
 *     public TreeNode(int val) {
 *         this.val = val;
 *         this.left = this.right = null;
 *     }
 * }
 */
public class Solution {
    /**
     * @param root: The root of the binary search tree.
     * @param value: Remove the node with given value.
     * @return: The root of the binary search tree after removal.
     */
    public TreeNode removeNode(TreeNode root, int value) {
        if (root == null)
            return null;
        if (value < root.val)
            root.left = removeNode(root.left, value);
        else if (value > root.val)
            root.right = removeNode(root.right, value);
        else {
            if (root.left == null)
                return root.right;
            if (root.right == null)
                return root.left;
            TreeNode x = root;
            root = findMin(root.right);
            root.right = deleteMin(x.right);
            root.left = x.left;
        }
        return root;
    }
}