1. Two Sum

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


-------------------------or ----------------------------------------------

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