gist for leetcode 572

subTreeOfAnotherTree.java

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public boolean isSubtree(TreeNode s, TreeNode t) {
        return traverse(s,t);
    }
    
    private boolean traverse(TreeNode s, TreeNode t) {
        return s != null && (equal(s,t) || traverse(s.left, t) || traverse(s.right,t));
    }
    
    private boolean equal(TreeNode sNode, TreeNode tNode) {
        if(sNode == null && tNode == null) {
            return true;
        }
        else if(sNode == null || tNode == null) {
            return false;
        }
        
        return sNode.val == tNode.val && equal(sNode.left, tNode.left) && equal(sNode.right, tNode.right);
    }
}