第一个只出现一次的字符

 1 char FirstNotRepeatingChar(char* pstr)
 2 {
 3     if (pstr == NULL)
 4     {
 5         return ‘\0‘;
 6     }
 7     const int HashTableSize = 256 ;
 8     int HashTable[HashTableSize] ;
 9 
10     for (int i = 0 ; i < HashTableSize ; i++)
11     {
12         HashTable[i] = 0 ;
13     }
14     char* pHashKey = pstr ;
15     while ( *pHashKey != ‘\0‘)
16     {
17         HashTable[*(pHashKey++)]++ ;
18     }
19     pHashKey = pstr ;
20     while (*pHashKey != ‘\0‘)
21     {
22         if (HashTable[*pHashKey] == 1)
23         {
24             return *pHashKey ;
25         }
26         pHashKey++ ;
27     }
28     return ‘\0‘;
29 }