BM32 合并二叉树

/*
 * function TreeNode(x) {
 *   this.val = x;
 *   this.left = null;
 *   this.right = null;
 * }
 */

/**
 * 
 * @param t1 TreeNode类 
 * @param t2 TreeNode类 
 * @return TreeNode类
 */
function mergeTrees( t1 ,  t2 ) {
    // write code here
    function preOrder(root1, root2) {
        if(root1 === null){
            return root2
        }
        if(root2 === null){
            return root1
        }
        root1.val += root2.val
        root1.left = preOrder(root1.left, root2.left)
        root1.right = preOrder(root1.right, root2.right)
        return root1
    }
    return preOrder(t1, t2)
}
module.exports = {
    mergeTrees : mergeTrees
};