二叉树的后序遍历

递归解法

var result=[]
function postorderTraversal( root ) {
    // write code here
    if(root==null){return []}
    postorderTraversal(root.left)
    postorderTraversal(root.right)
    result.push(root.val)
    return result
}

迭代解法

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

/**
  * 
  * @param root TreeNode类 
  * @return int整型一维数组
  */
function postorderTraversal( root ) {
    // write code here
    var stack = []
    var result = []
    var current = root
    while(current || stack.length){
        while(current){
            result.push(current.val)
            stack.push(current.left)
            current = current.right
        }
        current = stack.pop()
    }
    return result.reverse()
}
module.exports = {
    postorderTraversal : postorderTraversal
};