TwoSum1.java

/**
 * Given an array of integers, return indices of the two numbers such that
 * they add up to a specific target.
 *
 * You may assume that each input would have exactly one solution, and
 * you may not use the same element twice.
 *
 * Example:
 * Given nums = [2, 7, 11, 15], target = 9,
 *
 * Because nums[0] + nums[1] = 2 + 7 = 9,
 * return [0, 1].
 */


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


public class TwoSum1 {

 public int[] twoSum(int[] nums, int target) {
 Map<Integer, Integer> foundSet = new HashMap<>();

 int[] returns = new int[2];
 for (int i = 0; i < nums.length; i++) {
 Integer now = nums[i];
 Integer lookingfor = target - now;
 if (foundSet.containsKey(lookingfor)) {
 returns[0] = foundSet.get(lookingfor);
 returns[1] = i;
 return returns;
 } else {
 foundSet.put(now, i);
 }
 }
 return returns;
 }

 public static void main(String[] args) {
 TwoSum1 ts = new TwoSum1();

 System.out.println(ts.twoSum(new int[]{2, 7, 11, 15}, 9));
 System.out.println(ts.twoSum(new int[]{1, 2, 3}, 5));
 }

}