LeetCode 1

### Description:

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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.

• 题意：
  输入一个数组和一个target，该数组中恰好有两个数和为target(数组中每个数只能使用一次)，返回这两个数的下标

• 思路：
  用字典解决， 将数组的值作为字典的key， 将数组的下标作为字典的value， 具体看代码

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Example:

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1. Given nums = [2, 7, 11, 15], target = 9,
   Because nums[0] + nums[1] = 2 + 7 = 9,
   return [0, 1].

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代码

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Golang

func twoSum(nums []int, target int) []int {
	num_map := make(map[int]int)
	for i, v := range nums {
		var ok bool
		var j int
		j, ok = num_map[target-v]
		if ok {
            return []int{j, i}
		} else {
            num_map[v] = i
		}
	}
	return nil
}

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