题目：
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
思路：
1.将数组存入hash中，以数组元素值为hash键，以数组元素索引为hash值
2.相同的数组元素，存储索引值大的元素
public class Solution {
public int[] twoSum(int[] numbers,int target) {
int[] result=new int[2]; //最终结果
//存储数组的的HashMap
HashMap<Integer,Integer> m=new HashMap<Integer,Integer>();
for(int i=0;i<numbers.length;i++) {
m.put(numbers[i],i);
}
for(int i=0;i<numbers.length;i++) {
int temp=target-numbers[i];
if(m.containsKey(temp)&&i<m.get(temp)) {
result[0]=i+1;
result[1]=m.get(temp)+1;
}
}
return result;
}
}
原文：http://www.cnblogs.com/hwu2014/p/4401870.html