TwoSum.java

package com.examplehub.leetcode.easy;

import java.util.HashMap;
import java.util.Map;

/** https://leetcode.com/problems/two-sum/ */
public class TwoSum {

  public static int[] solution1(int[] nums, int target) {
    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 null;
  }

  public static int[] solution2(int[] nums, int target) {
    Map<Integer, Integer> map = new HashMap<>();
    for (int i = 0; i < nums.length; i++) {
      int complement = target - nums[i];
      if (map.containsKey(complement)) {
        return new int[] {map.get(complement), i};
      }
      map.put(nums[i], i);
    }
    return null;
  }
}