package com.matao.easy;

import java.util.Arrays;
import java.util.HashMap;

/**
 * Created by matao on 2018/9/30.
 * <p>
 * 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.
 * <br><br>
 * Example:
 * Given nums = [2, 7, 11, 15], target = 9,
 * Because nums[0] + nums[1] = 2 + 7 = 9,
 * return [0, 1].
 */
public class TwoSum {

    public static int[] twoSum(int[] nums, int target) {
        HashMap<Integer, Integer> map = new HashMap<Integer, Integer>();
        for (int i = 0; i < nums.length; i++) {
            int diff = target - nums[i];
            if (map.containsKey(diff)) {
                return new int[]{map.get(diff), i};
            }
            map.put(nums[i], i);
        }
        throw new IllegalArgumentException("No two sum solution");
    }

    public static void main(String[] args) {
        int[] nums = {2, 7, 11, 15};
        int[] result = twoSum(nums, 9);
        System.out.println(Arrays.toString(result));
    }
}

package com.matao.easy;

import java.util.Arrays;
import java.util.HashMap;

/**
 * Created by matao on 2018/9/30.
 * <p>
 * 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.
 * <br><br>
 * Example:
 * Given nums = [2, 7, 11, 15], target = 9,
 * Because nums[0] + nums[1] = 2 + 7 = 9,
 * return [0, 1].
 */
public class TwoSum {

    public static int[] twoSum(int[] nums, int target) {
        HashMap<Integer, Integer> map = new HashMap<Integer, Integer>();
        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);
        }
        throw new IllegalArgumentException("No two sum solution");
    }

    public static void main(String[] args) {
        int[] nums = {2, 7, 11, 15};
        int[] result = twoSum(nums, 9);
        System.out.println(Arrays.toString(result));
    }
}

rename local variable