Leetcode 1 - Two Sum

Problem 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].

Java:

class Solution {
    public int[] twoSum(int[] nums, int target) {
        HashMap map = new HashMap<>();
        
        for (int i = 0; i < nums.length; i++) {
            if(map.containsKey(target - nums[i])) {
                return new int[] {map.get(target - nums[i]), i};
            } else {
                map.put(nums[i], i);
            }
        }
        
        return new int[]{0, 0};
    }
}

Python:

class Solution:
    def twoSum(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: List[int]
        """
        dic = {}
        for i, num in enumerate(nums):
            if num in dic:
                return dic[num], i
            else:
                dic[target - num] = i

Go:

func twoSum(nums []int, target int) []int {
    m := make(map[int]int)
    
    for i := 0; i < len(nums); i++ {
        if v, ok := m[nums[i]]; ok {
            return [] int { v, i }
        } else {
            m[target - nums[i]] = i
        }
    }
    
    return []int{0, 0}
}