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.
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public class Solution { public int[] twoSum(int[] nums, int target) { Map<Integer, Integer> numToIndex = new HashMap<Integer,Integer>(); for(int i = 0; i<nums.length; ++i) { numToIndex.put(nums[i], i); } for(int i = 0; i<nums.length; ++i) { Integer otherIndex = numToIndex.get(target-nums[i]); if(otherIndex!=null && i != otherIndex) return new int[]{i, otherIndex}; } return new int[2]; } }
原文：http://www.cnblogs.com/neweracoding/p/5261656.html