LeetCode - 1. Two Sum #Java

Question

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.
Example:
Given nums = [2, 7, 11, 15], target = 9,Because nums[0] + nums[1] = 2 + 7 = 9,return [0, 1].
**UPDATE (2016/2/13):
**The return format had been changed to zero-based indices. Please read the above updated description carefully.

Solutions

渣渣表示只会用for循环，就不贴出O(n^2)的弱逼算法了。
去讨论区学习了下，大大们都用的HashMap，我去，HashMap这么高端的东西我长这么大一次都没用过啊！看看了思路，我觉得我是不是要转职了，没法混啊！

public class Solution {
    public int[] twoSum(int[] nums, int target) {
        HashMap<Integer, Integer> map = new HashMap<Integer, Integer>();
        int[] result = null;
        
        for (int i = 0; i < nums.length; i++) {
            if (!map.containsKey(nums[i])) {
                map.put(target - nums[i], i);
            } else {
                int index = map.get(nums[i]);
                result = new int[]{index, i};
                break;
            }
        }
        
        return result;
    }
}

TO DO

• 教练！我要学HashMap！