Java

# Java 

1. Brute-Force Approach :

class Solution 
{
    public int[] twoSum(int[] nums, int target) 
    {
        int n=nums.length,i,j;
        int[] arr=new int[2];
        for(i=0;i<n;i++)
        {
            for(j=i+1;j<n;j++)
            {
                if(nums[i]+nums[j]==target)
                {
                    arr[0]=i;
                    arr[1]=j;
                    break;
                }
            }
        }
        return arr;
    }
}

2. Optimal Approach : (Hashmap)

class Solution 
{
    public int[] twoSum(int[] nums, int target) 
    {
        int[] arr=new int[2];
        HashMap<Integer,Integer> map=new HashMap<>();
        int i,n=nums.length,num,diff;
        for(i=0;i<n;i++)
        {
            num=nums[i];
            diff=target-num;
            if(map.containsKey(diff))
            {
                arr[0]=map.get(diff);
                arr[1]=i;
            }
            else
            {
                map.put(nums[i],i);
            }
        }
        return arr;
    }
}