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, and you may not use the same element twice.
Example:
Given nums = [2, 7, 11, 15], target = 9, Because nums[0] + nums[1] = 2 + 7 = 9, return [0, 1].
public class Solution {public int[] TwoSum(int[] nums, int target) {if (nums == null || nums.Length < 1) {return null;}Dictionary<int, int> dict = new Dictionary<int, int>();for (int i = 0; i < nums.Length; i++) {if (dict.ContainsKey(target - nums[i])) {int[] arr = { dict[target - nums[i]], i};return arr;} else {dict[nums[i]] = i;}}return null;}}
原文：http://www.cnblogs.com/xiejunzhao/p/fcf932b1763ef76888dded0cf4fee9d3.html