力扣1. 两数之和

 1 class Solution {
 2     public int[] twoSum(int[] nums, int target) {
 3        // 暴力法
 4        for(int i = 0; i < nums.length; i++){
 5            for(int j = i + 1; j < nums.length; j++){
 6                if(nums[i] + nums[j] == target){
 7                    return new int[] {i, j};
 8                }
 9            }
10        }
11        return null;
12     }
13 }

 1 class Solution {
 2     public int[] twoSum(int[] nums, int target) {
 3         HashMap<Integer, Integer> map = new HashMap<>();
 4         for(int i = 0; i < nums.length; i++){
 5             int another = target - nums[i];
 6             if(map.containsKey(another)){
 7                 int j = map.get(another);
 8                 return new int[] {j, i};
 9             }else{
10                 map.put(nums[i], i);
11             }
12         }
13         return null;
14     }
15 }