Easy to understand Java recursive solution


  • 0
    /**
     * Definition for a binary tree node.
     * public class TreeNode {
     *     int val;
     *     TreeNode left;
     *     TreeNode right;
     *     TreeNode(int x) { val = x; }
     * }
     */
    public class Solution {
        public int getMinimumDifference(TreeNode root) {
            int diffLeft = Integer.MAX_VALUE;
            int diffRight = Integer.MAX_VALUE;
            if(root.left == null && root.right == null) return Math.min(diffLeft, diffRight);
            if (root.left != null) {
                diffLeft = Math.min(getMin(root, root.left, diffLeft),getMinimumDifference(root.left));
            }
            if (root.right != null) {
                diffRight = Math.min(getMin(root, root.right, diffRight),getMinimumDifference(root.right));
            }
            return Math.min(diffLeft, diffRight);
        }
        
        private int getMin(TreeNode first, TreeNode second, int diff) {
            if(first == null || second == null) {
                return diff;
            }
            else {
                diff = Math.abs(first.val - second.val);
                if(second.left != null) {
                    diff = Math.min(diff, getMin(first, second.left, diff));
                }
                if(second.right != null) {
                    diff = Math.min(diff, getMin(first, second.right, diff));
                }
                return diff;
            }
        }
    }
    

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