[Go] LeetCode 1. Two Sum

Description

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].

Solution

/* [Go]  1.Brute Force O(n2) */
func twoSum(nums []int, target int) []int {
 for i := 0; i < len(nums); i++{
  for j := i + 1; j < len(nums); j++{
   if nums[j] == target - nums[i]{
    return []int{i,j}
   }
  }
 }
 return nil
}
/* [Go] 2. Two-pass Hash Table O(n)  point: using complement*/
func twoSum(nums []int, target int) []int {
 indexMap := make(map[int]int)
 for i := 0; i < len(nums); i++ {
  indexMap[nums[i]] = i
 }
 for i := 0; i < len(nums); i++ {
  complement := target - nums[i]
  if _,ok := indexMap[complement]; ok && indexMap[complement] != i{
   return []int{i,indexMap[complement]}
  }
 }
 return nil
}
/* [Go] 3. One-pass Hash Table O(n)  point: using complement*/
func twoSum(nums []int, target int) []int{
    indexMap := make(map[int]int)
    for i := 0; i < len(nums); i++ {
        complement := target - nums[i]
        if _,ok := indexMap[complement]; ok {
            return []int{i,indexMap[complement]}
        }
        indexMap[nums[i]] = i
    }
    return nil
}

I want to write the test code later.