题解

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

哈希表

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

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

Java中return new int[0]的含义