题解 | #字符流中第一个不重复的字符#

#include <functional>
#include <unordered_map>
class Solution
{
public:
  //Insert one char from stringstream
    void Insert(char ch) {
         hash_map[ch] += 1;
         str += ch;

    }
  //return the first appearence once char in current stringstream
    char FirstAppearingOnce() {
        for (int i = 0; i < str.length(); ++i) {
            if (hash_map[str[i]] == 1) {
                return str[i];
            }
        }
        return '#';
    }
private:
    string str;
    std::unordered_map<char, int> hash_map;
};

把hash map用好即可