kingdow-liu

二叉树遍历有前、中、后序遍历三种，用递归法解决没什么意思，解题过程中会忽略很多的东西，下面我们用栈模拟这个递归的过程。前序遍历遍历流程：根 -> 左 -> 右public static List<Integer> preorderTraversal(TreeNode root){ List<Integer> res = new LinkedList<>(); if(root == null){

1. 两数之和class Solution: def twoSum(self, nums, target): new_nums = sorted(nums) end = 0 for num in new_nums: if num == target/2 and new_nums[end+1] == target/2...