題目描述

輸出描述:

如果當前字元流沒有存在出現一次的字元，返回#字元。

思路：
模擬雜湊

class Solution
{
  public:
    //Insert one char from stringstream
    string str;
    int hash[256] = {0};
    void Insert(char
 
 ch)
    {
        str += ch;
        hash[ch]++;
    }
    //return the first appearence once char in current stringstream
    char FirstAppearingOnce()
    {
        for (int i = 0; i < str.size(); i++)
        {
            if (hash[str[i]] == 1)
                return str[i];
        }
        return
 
 '#';
    }
};