一道Google面试题的新解法探索

#include <iostream>
#include <string>

using namespace std;
char* first_once_letter(char* input)
{
char* p1 = input;
char* p2 = input;
const int hash_size = 255;
int hash[hash_size] ={0};
while(*p1 != '\0')
{
hash[*p1]++;              //a b a c c d e f f
//        p1
if(hash[*p1] != 1)        //  p2
p2++;
p1++;
}
return p2;
}
int main(void)
{
char* s = "abaccdeff";
char* k = first_once_letter(s);
cout << *k << endl;
return 0;
}