leetcode 刷题 数组类 Two Sum

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Two Sum 

Given an array of integers ,find two numbers such that they add up to a specific target number.

The function twoSum should  return  inclices of the two numbers such that they add up to the target ,where

index1 must be less than  index2.Please note that your returned answers (both index1 and index2) 

are not zero-based.

You must assume that each input would have exactly one solution.

Input :number ={2,7,11,15},target =9;

Output :index1=1,index2=2

给定一个整数数组，找到两个数字，这样它们就可以加到一个特定的目标数。
函数二和应该返回两个数字的inclices，它们加起来到目标，在哪里。
index1必须小于index2。请注意您返回的答案(包括index1和index2)
不是从零开始的。
您必须假定每个输入都只有一个解决方案。
输入:数量= { 2、7、11、15 },目标= 9;
输出:index1 = 1,index2 = 2

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public int[] twoSum(int[] nums, int target) {
        if (nums == null || nums.length <= 1) {
            return new int[2];
        }
        Map<Integer, Integer> map = new HashMap<Integer, Integer>();
        // key = target - nums[i], just one solution
        for (int i = 0; i < nums.length; i++) {
            map.put(target - nums[i], i);
        }
        for (int i = 0; i < nums.length; i++) {
            Integer v = map.get(nums[i]);
            // can't use itself
            if (v != null && v != i) {
                return new int[] { i + 1, v + 1 };
            }
        }
        return null;
    }