Leet Code OJ 1. Two Sum [Difficulty: Easy]

题目： 
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].

翻译： 
给定一个整形数组和一个整数target，返回2个元素的下标，它们满足相加的和为target。 
你可以假定每个输入，都会恰好有一个满足条件的返回结果。
Java版代码1（时间复杂度O(n)）：

public class Solution {
    public int[] twoSum(int[] nums, int target) {
        Map map=new HashMap<>();
        for(int i=0;i

Java版代码2（时间复杂度O(n^2)）：

public class Solution {
    public int[] twoSum(int[] nums, int target) {
        int[] result=new int[2];
        for(int i=0;i