package amazon;

// 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;

/**

* Created by anduo on 17-3-13.

*/

public class TwoSum {

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

if (nums == null || nums.length == 0) {

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

}

// 有一个map记录前面的值在数组中的位置，这样遍历的是否就可以找到target - nums[i] 的位置

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

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

int key = target - nums[i];

if (map.containsKey(key)) {// 找到答案了

return new int[]{map.get(key) + 1, i + 1};

}

map.put(key, i);

}

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

}

}