LeetCode -- Single Number

题目描述：


Given an 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?


在一个数列中找到没有重复的那一个。


思路：哈希表统计次数




实现代码：

public class Solution {
    public int SingleNumber(int[] nums) {
        var hash = new Dictionary<int,int>();
        for(var i = 0;i < nums.Length; i++){
            if(!hash.ContainsKey(nums[i])){
                hash.Add(nums[i],1);
            }
            else{
                hash[nums[i]]++;
            }
        }
        
        foreach(var k in hash.Keys){
            if(hash[k] == 1){
                return k;
            }
        }
        
        return -1;
    }
}