1. two sum

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].

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

Ways of generating java arrays:

1. 

int[] i = new int[] {0,1};

2.

int i = new int[3];

3.

int[] i = {1,2,3};