C#版 - Leetcode 136. Single Number题解

Input: [2,2,1]
Output: 1

Input: [4,1,2,1,2]
Output: 4

public class Solution {
    public int SingleNumber(int[] nums) {
            int res = 0;
            Dictionary<int, int> dict = new Dictionary<int, int>();
            foreach (var num in nums)
            {
                if (!dict.ContainsKey(num))
                {
                    dict.Add(num, 1);
                }
                else
                    dict[num]++;
            }

            res = dict.FirstOrDefault(kv => kv.Value == 1).Key;

            return res;
    }
}