public int[] twoSum(int[] numbers, int target) {
        // Start typing your Java solution below
        // DO NOT write main() function
    	if(numbers == null || numbers.length < 2)
    		return null;
    	
    	HashMap<Integer, Integer> diffMap = new HashMap<Integer, Integer>();
    	for(int i=0; i<numbers.length; i++){
    		if(numbers[i] < target){
    			Integer beforeIdx = diffMap.get(numbers[i]);
    			if(beforeIdx != null){
    				return new int[]{beforeIdx, i + 1};
    			}
    			
    			diffMap.put(target-numbers[i], i + 1);
    		}
    	}
    	
    	
    	return null;
    
    	
        
    }