其实我不知道这道题的point是什么…………

两种方法，hashmap/ two pointers

HashMap

1     public int[] twoSum(int[] numbers, int target) { 2         if(numbers.length == 0) { 3             return null; 4         } 5         int[] res = new int[2]; 6         Map
     
       map = new HashMap
      
       (); 7         for(int i = 0; i < numbers.length; i++) { 8             if(!map.containsKey(target - numbers[i])) { 9                 map.put(numbers[i], i);10             } else {11                 res[0] = map.get(target - numbers[i]) + 1;12                 res[1] = i + 1;13                 return res;14             }15         }16         return res;17     }
      
     

 

 

 

Two pointers

1     public int[] twoSum(int[] numbers, int target) { 2         if(numbers.length == 0) { 3             return null; 4         } 5         int[] res = new int[2]; 6         int walker = 0; 7         int runner = numbers.length - 1; 8         int sum = numbers[walker] + numbers[runner]; 9         while(sum != target) {10             if(sum > target) {11                 runner--;12             } else {13                 walker++;14             }15             sum = numbers[walker] + numbers[runner];16         } 17         res[0] = walker + 1;18         res[1] = runner + 1;19         return res;20     }