101-symmetric-tree.js

/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 * @return {boolean}
 */
var isSymmetric = function(root) {
    
 
    
   return !root||hepler(root.right,root.left);
    
};


function hepler(left,right){
    
    if(!left&&!right) return true;
    if(!left||!right) return false;
    
   return(left.val==right.val)&&
        hepler(right.right,left.left)&&
        hepler(left.right,right.left)

   
  

     

}