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].
UPDATE (2016/2/13):
The return format had been changed to zero-based indices. Please read the above updated description carefully.

思路:

• 题意：给定一个互不相同的整数数组nums，给定一个目标值target，求两个索引值，相应的值的和等于target
• 首先排除nums == null和nums.length < 2,返回null，至于其他的情况可以用两个循环解决

代码：

public class Solution {
    public int[] twoSum(int[] nums, int target) {
        int[] result = new int[2]; 
        int n = nums.length;
        if(n < 2 || nums == null){
            return null;
        }
        for(int i = 0;i < n;i++){
            for(int j = i+1;j < n;j++){
                if(nums[i] + nums[j] == target){
                    result[0] = i;
                    result[1] = j;
                    return result;
                }
            }
        }
        return null;
    }
}