第一个只出现一次的字符

题目描述

#include <iostream>

using namespace std;

char FirstNoRepeatingChar(char* pString)
{
	if(pString == NULL)
		return '\0';
	const int tableSize = 256;

	unsigned int HashTable[tableSize];

	for(int i= 0; i < 256;i++)
	{
		HashTable[i] = 0;
	}

	char* pHashKey = pString;

	while(*pHashKey != '\0')
	{
		HashTable[*(pHashKey)]++;
		pHashKey++;
	}
	pHashKey = pString;
	while(*pHashKey != '\0')
	{
		if(HashTable[*(pHashKey)] == 1)
			return *(pHashKey);
		pHashKey++;
	}
	return '\0';
}

// ====================测试代码====================
void Test(char* pString, char expected)
{
    if(FirstNoRepeatingChar(pString) == expected)
        printf("Test passed.\n");
    else
        printf("Test failed.\n");
}

int main(int argc, char* argv[])
{
    // 常规输入测试，存在只出现一次的字符
    Test("google", 'l');

    // 常规输入测试，不存在只出现一次的字符
    Test("aabccdbd", '\0');

    // 常规输入测试，所有字符都只出现一次
    Test("abcdefg", 'a');

    // 鲁棒性测试，输入NULL
    Test(NULL, '\0');

    return 0;
}