Solution.java

package com.leetcode.minji;

import java.util.HashMap;

/**
 * 1. Two Sum
 * https://leetcode.com/problems/two-sum/submissions/
 */
class Solution {
    public int[] twoSum(int[] nums, int target) {
        int[] result = new int[2];
        for (int i = 0; i < nums.length - 1; i++) {
            for (int j = i + 1; j < nums.length; j++) {
                if (nums[i] + nums[j] == target) {
                    return new int[]{i, j};
                }
            }
        }
        return result;
    }

    public int[] twoSum2(int[] nums, int target) {
        HashMap<Integer, Integer> map = new HashMap<>();
        for (int i = 0; i < nums.length; i++) {
            map.put(nums[i], i);
        }

        for (int i = 0; i < nums.length; i++) {
            if (map.containsKey(target - nums[i]) && i != map.get(target - nums[i])) {
                return new int[]{i, map.get(target - nums[i])};
            }
        }
        return new int[]{};
    }
}