C语言之字符串反转

1.编写一个函数使字符串逆序：

输入：abcdef
输出：fedcba

法一：递归

#include
#include
void reverse(char* s)
{
	int n = strlen(s);
	if (n > 1)
	{
		char c = *s;
		*s = *(s + n - 1);
		*(s + n - 1) = '\0';
		reverse(s + 1);
		*(s + n - 1) = c;
	}
}
int main()
{
    char s[] = "abcdef";
	printf("逆置前:%s\n", s);
	reverse(s);
	printf("逆置后:%s\n", s);
	return 0;
}

法二：指针

#include
#include
void reverse(char* s)
{
	char* left = s;
	char* right = s + strlen(s) - 1;
    while (left < right)
	{
		char tmp = *left;
		*left = *right;
		*right = tmp;


		left++;
		right--;
	}
}
int main()
{
    char s[] = "abcdef";
	printf("逆置前:%s\n", s);
	reverse(s);
	printf("逆置后:%s\n", s);
	return 0;
}

2.编写一个函数倒置句子中的单词:

输入：I like beijing.
输出：beijing. like I

法一：常规思想

#include 
#include 
int main()
{
    char a[100] = { 0 };
    int len, i, j;
    scanf("%s", a);
    len = strlen(a);
    for (i = len - 1; i >= 0; i--)
    {
        if (a[i] == ' ')
        {
            for (j = i + 1; a[j] != '\0' && a[j] != ' '; j++)
                printf("%c", a[j]);
            printf(" ");
        }
    }
    i = 0;
    while (a[i] != ' ')
        i++;
    for (j = 0; j < i; j++)
        printf("%c", a[j]);
}

法二：投机取巧

#include
void reverse() 
{
    char a[101];
	if (scanf("%s", a) != EOF)
	{
		reverse();
		printf("%s ", a);
	}
}
int main() 
{
	reverse();
	return 0;
}