1. Two Sum
我的github有源码https://github.com/ttllpp/leetcode
题目
Given an array of integers, return indices of the two numbers such that they add up to a specific target.
You may assume that each input would have exactly one solution, and you may not use the same element twice.
Example:
Given nums = [2, 7, 11, 15], target = 9,
Because nums[0] + nums[1] = 2 + 7 = 9,
return [0, 1].解题思路1
a + b = target也可以看成是
a = target - b然后依次寻找差值a
解题思路2
a + b = target最暴力的方法，直接两个循环
解题思路3
a + b = target也可以看成是
a = target - b在map[整数]整数的序号中，可以查询到a的序号。这样就不用嵌套两个for循环了。