Given a non-empty array of integers nums, every element appears twice except for one. Find that single one.
You must implement a solution with a linear runtime complexity and use only constant extra space.
Example:
Input: nums = [2,2,1]
Output: 1
Input: [4,1,2,1,2]
Output: 4
找出陣列中只出現過一次的數字，這題直覺性的應該會使用Directory，首先判斷Key存不存在，如果存在value + 1，不存在的話把數字新增至Key裡面並且給予值 1，最後判斷Directory裡面Value等於1的值，回傳Key就好了。
public class Solution {
public int SingleNumber(int[] nums) {
Dictionary<int, int> dic = new Dictionary<int, int> { };
for (int i = 0; i < nums.Length; i++)
{
if (dic.ContainsKey(nums[i]))
{
dic[nums[i]]++;
}else
{
dic.Add(nums[i], 1);
}
}
if (dic.ContainsValue(1))
{
return dic.FirstOrDefault(x => x.Value == 1).Key;
}
else
{
return 0;
}
}
}