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.
Given nums = [2, 7, 11, 15], target = 9, Because nums + nums = 2 + 7 = 9, return [0, 1].
My first version:
nested two for loops, find the two value sum == target
My second version:
also two loops: the first loop is the same, but the second loop starts from x+1, no need to start index 0.