有一个字符数组的内容为:“student a am i”,
请你将数组的内容改为"i am a student".
要求:
不能使用库函数。
只能开辟有限个空间(空间个数和字符串的长度无关)。
提示:(先逆置整个字符串,再逆置每个单词)
student a am i
i ma a tneduts
i am a student
#include<stdio.h>
#include<Windows.h>
int MyStrlen(char *str)
{
int count = 0;
while (*str != 0)
{
count++;
str++;
}
return count;
}
void reverse(char *left, char *right)
{
char tmp;
while (left < right)
{
tmp = *left;
*left = *right;
*right = tmp;
left++;
right--;
}
}
void ReverseStr(char *str)
{
char *left = str;
char *right = str + MyStrlen(str) - 1;
char *cur = str;
reverse(left, right);//逆置字符串
while (*cur!='\0')
{
char *start = cur;
while (*cur != ' '&&*cur != '\0')
{
cur++;
}
reverse(start,cur-1);
if (*cur == ' ')
{
cur++;
}
}
}
int main()
{
char str[] = "student a am i" ;
ReverseStr(str);
printf("%s\n", str);
system("pause");
return 0;
}
使用库函数的标准做法:
#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
void reverve_swap(char *left, char *right)
{
assert(left != NULL); //断言不是空指针
assert(right != NULL);
while (left < right)
{
char tmp = *left;
*left = *right;
*right = tmp;
left++;
right--;
}
}
char *reverve(char *p)
{
int len = strlen(p);
char *start = p;
char *end = NULL;
char *ret = p;
reverve_swap(p, p + len - 1); //逆序整个字符串
while (*p)
{
start = p;
while ((*p != ' ') && (*p != '\0')) //找到一块单词
{
p++;
}
end = p - 1;
reverve_swap(start, end);//逆序单个单词
if (*p == ' ') //找到空格
p++;
}
return ret;
}
int main()
{
char arr[] = "student a am I";
printf("交换前:%s\n", arr);
printf("交换后:%s\n", reverve(arr));
system("pause");
return 0;
}