leetcode------Two Sum

标题：	Two Sum
通过率：	17.9%
难度：	中等

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

The function twoSum should return indices 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 may assume that each input would have exactly one solution.

Input: numbers={2, 7, 11, 15}, target=9
Output: index1=1, index2=2

利用map储存遍历过的元素，然后每次查看是否有target元素。如果有则查找完成，注意题干说明是从1开始，代码如下：

public class Solution {
    public int[] twoSum(int[] numbers, int target) {
        Map<Integer,Integer> map=new HashMap<Integer,Integer>();
        for(int i=0;i<numbers.length;i++){
            int x=numbers[i];
            if(map.containsKey(target-x)){
                return new int[]{map.get(target-x)+1,i+1};
            }
            map.put(x,i);
        }
        return null;
        
    }
}