<1>声明提前：
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1.var声明的变量无法通过delete删除
Given s1, s2, s3, find whether s3 is formed by the interleaving of s1 and s2.
Given a string containing only digits, restore it by returning all possible valid IP address combinations.
1.数组初始化表达式：
Given an array of integers where 1 ≤ a[i] ≤ n (n = size of array), some elements appear twice and others appear once.
Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).
Given a binary tree, return the inorder traversal of its nodes’ values.
Suppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand.
Given a set of distinct integers, nums, return all possible subsets.Note: The solution set must not contain duplicate subsets.For example,