Programming Algorithm-the first character code that appears only once (c)

Source: Internet
Author: User
The first character code that appears only once (c)


Question: Find the first character that appears only once in the string.

The character is of the char type, so it matches256 typesPossible, useHash table, Calculate the number of occurrences, and then find the first occurrence of characters.


/* * main.cpp * *  Created on: 2014.6.12 *      Author: Spike *//*eclipse cdt, gcc 4.8.1*/#include <stdio.h>#include <stdlib.h>#include <string.h>char FirstNotRepeatingChar (char* pString) {if (pString == NULL)return ‘\0‘;const int tableSize = 256;unsigned int hastTable[tableSize];for (unsigned int i=0; i<tableSize; ++i)hastTable[i] = 0;char* pHashKey = pString;while (*pHashKey != ‘\0‘)hastTable[*(pHashKey++)]++;pHashKey = pString;while (*pHashKey != ‘\0‘) {if (hastTable[*pHashKey] == 1)return *pHashKey;pHashKey++;}return ‘\0‘;}int main(void){char pString[] = "abaccdeff";char result =  FirstNotRepeatingChar (pString);    printf("result = %c\n", result);    return 0;}


result = b

Contact Us

The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion; products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the content of the page makes you feel confusing, please write us an email, we will handle the problem within 5 days after receiving your email.

If you find any instances of plagiarism from the community, please send an email to: and provide relevant evidence. A staff member will contact you within 5 working days.

A Free Trial That Lets You Build Big!

Start building with 50+ products and up to 12 months usage for Elastic Compute Service

  • Sales Support

    1 on 1 presale consultation

  • After-Sales Support

    24/7 Technical Support 6 Free Tickets per Quarter Faster Response

  • Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.