public class Solution {    public int[] twoSum(int[] nums, int target) {         /* Basic idea: Load the array into a hashMap with the value of each array element as key and index of the array as value           Interate through the key, and check whether "target - value" is in the map.            Save the array index and sort it                      Special case: The array contains duplicate elements.             1) The target value is not or only related to the one of the duplicate value => store the first one.           2) The target value is twice of the duplicate value => directly store the two indexes and return output.        */                int[] results = new int[2];        Map
     
       numsMap = new HashMap
      
       ();        for (int i = 0; i < nums.length; i++){            if (numsMap.containsKey(nums[i])){                /*It has duplicated number                 if 1) duplication is the results, return                    2) drop the second, if it is put back to the map, value(index) got overide */                if (2 * nums[i] == target){                    results[0] = numsMap.get(nums[i]); // it stores as index when the Hash is created                    results[1] = i + 1;  // i start at 0, so need to +1 as index                    return results;                }             } else {                numsMap.put(nums[i], i+1); //the array index start at 0;            }        }                for(Integer key : numsMap.keySet()){            if (numsMap.containsKey(target - key)){                int a = numsMap.get(key);                int b = numsMap.get(target-key);                if (a < b){                    results[0] = a;                    results[1] = b;                } else {                    results[0] = b;                    results[1] = a;                }            }        }        return results;    }}