小麦大大博客

1、Two Sum 两数之和案例：Given nums = [2, 7, 11, 15], target = 9,Because nums[0] + nums[1] = 27 = 9, return [0, 1]思路：使用一个HashMap，来建立数字和其坐标位置之间的映射，我们都知道HashMap是常数级的查找效率，这样，我们在遍历数组的时候，用target减去遍历到的数字，...

验证回文数字例子Example 1:Input: 121Output: trueExample 2:Input: -121Output: falseExplanation: From left to right, it reads -121. From right to left, it becomes 121-. Therefore it is not a palindrome....