112.路径总和

//通过递归方法来解决
var hasPathSum = function(root, targetSum) {
    if(!root) {
        return false;
    }
    if(root.val == targetSum&&root.left == null &&root.right == null) {
        return true;
    } 
    let left = hasPathSum(root.left, targetSum - root.val);
    let right = hasPathSum(root.right, targetSum - root.val);
    return left||right;
};