C#刷遍 LeetCode 系列 - No.136. Single Number - 题解

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C#版 - Leetcode 136. Single Number - 题解

136. Single Number

在线提交: https://leetcode.com/problems/single-number/

Given a non-empty array of integers, every element appears twice except for one. Find that single one.

Note:

Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?

Example 1:

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

Example 2:

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

思路: 使用 Dictionary<int, int>存储每一个整数出现的次数即可，然后从里面挑出第一个出现次数为 1 的 KeyValuePair 的 Key 值。

已 AC 代码:

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;
    }
}

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