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:
代码语言：javascript复制Given nums = [2, 7, 11, 15], target = 9,
Because nums[0] nums[1] = 2 7 = 9,
return [0, 1].
