package kent.alg.leetcode.Array;

import java.util.HashMap;

/**

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.

EX:

Given nums = [2, 7, 11, 15], target = 9,

Because nums[0] + nums[1] = 2 + 7 = 9,

return [0, 1].

Time: O(n)

Space: O(n)

* @author kentfan

*/

public class TwoSum {

public static int[] twoSum(int[] nums, int target) {

// error handling

if(nums == null || nums.length < 2)

return new int[] {-1,-1};

int[] result = new int[] {-1, -1};

HashMap<Integer, Integer> map = new HashMap<>();

for(int i=0; i< nums.length; i++) {

if(map.containsKey(target - nums[i])) {

result[0] = map.get(target - nums[i]);

result[1] = i;

break;

}

map.put(nums[i], i); //算過的值，都放到map。

}

return result;

}

public static void main(String[] args) {

int[] nums = {2, 7, 11, 15};

int target = 18;

System.out.println(twoSum(nums, target)[0] + "," + twoSum(nums, target)[1]);

}

}