var?sumOfLeftLeaves?=?function(root)?{
????????if(root==null)?return?0;
????????return?sumOfLeftLeaves(root.left)+?sumOfLeftLeaves(root.right)+?(root.left!=null??&&?root.left.right==null&&root.left.left==null???root.left.val?:?0);
};
找到左葉子節(jié)點(diǎn)：沒(méi)有l(wèi)eft和right复唤，遞歸查找
