#include <stdio.h>

void reverse(char *pStr)   //逆序
{
	int left = 0;
	int right= strLen(pStr) - 1;
	
	while (left < right)
	{
		char tmp     = pStr[left];
		pStr[left++] =pStr[right];
		pStr[right--]=tmp;
	}
}

int strLen(char *pStr)//求長度
{
	if (pStr == NULL)
		return -1;
	
	int len = 0;
	
	while(*pStr++)//while(*pStr != '\0') 或者while(*pStr)	
	{
		len++;    //len++;pStr++;
	}
	
	return len;
}

int main()
{
	char str[100] = "hello world";
	int len = strLen(str);
	
	printf("len = %d\n", len);
	
	reverse(str);
	printf("%s\n",str);
	
    return 0;
}