1.找两个数下标Two Sum

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].
用字典，存储当前值的下标，判断是否存在target - nums[i]
  1. public class Solution {
  2.     public int[] TwoSum(int[] nums, int target) {
  3. 		if (nums == null || nums.Length < 1) {
  4. 			return null;
  5. 		}
  6. 		Dictionary<int, int> dict = new Dictionary<int, int>();
  7. 		for (int i = 0; i < nums.Length; i++) {
  8. 			if (dict.ContainsKey(target - nums[i])) {
  9. 				int[] arr = { dict[target - nums[i]], i};
  10. 				return arr;
  11. 			} else {
  12. 				dict[nums[i]] = i;
  13. 			}
  14. 		}
  15. 		return null;
  16.     }
  17. }





posted @ 2017-02-01 22:58  xiejunzhao  阅读(159)  评论(0)  编辑  收藏  举报