C language: use a pointer to reverse the order of a string

topic:

Link: Reverse order of characters__Niuke.com
Source: Niuke.com
           

Reverse the contents of a string str and output it .

           

Enter a description:

Enter a string , may have spaces

             

Output description:

output string in reverse order

         

Example 1

enter

I am a student

output

tneduts a ma I

Example 2

enter

nowcoder

output

redocwon

                    

 =========================================================================

                       

Ideas:

general idea:

(one).

Create character array str :

char str[10001] = { 0 };

         

Enter string :

gets(str); --Input array data , gets can also read spaces

         

Find the length of the input string :

int len ​​= strlen(str); -- use the strlen() function to get the length of the string , the header file <string.h> needs to be included

              

(two).

For reverse order : use the left and right pointers left and right

        

Create left and right pointers :

char* left = str; -- left pointer

char* right = str + len -1; --right pointer

         

Use the while loop with the left and right pointers to reverse the string :

The idea of ​​using pointer reverse order is the same as the idea of ​​using subscript reverse order .

Swapping two elements requires a temporary variable ,

Adjust the position of the pointer once exchanged

                

---

                 

first step:

（1）.

Create character array str :

char str[10001] = { 0 };

         

（2）.

Enter string :

gets(str); --Input array data , gets can also read spaces

               

（3）.

Find the length of the input string :

int len ​​= strlen(str); -- use the strlen() function to get the length of the string , the header file <string.h> needs to be included

                     

Implementation code:

#include <stdio.h>
#include <string.h>
int main()
{
	//创建 字符数组str :
	char str[10001] = { 0 };

	//输入字符串：
	gets(str); //输入数组数据，gets可以把空格也读入
	
	//求输入的字符串长度：
	int len = strlen(str); //记得包含头文件<string.h>


	return 0;
}

Realize the picture:

                 

---

                 

Step two:

For reverse order : use the left and right pointers left and right

           

（1）.

Create left and right pointers :

char* left = str; -- left pointer

char* right = str + len -1; --right pointer

         

（2）.

Use the while loop with the left and right pointers to reverse the string :

The idea of ​​using pointer reverse order is the same as the idea of ​​using subscript reverse order .

Swapping two elements requires a temporary variable ,

Adjust the position of the pointer once exchanged

                     

（3）.

to print

               

Implementation code:

#include <stdio.h>
#include <string.h>
int main()
{
	//创建 字符数组str :
	char str[10001] = { 0 };

	//输入字符串：
	gets(str); //输入数组数据，gets可以把空格也读入
	
	//求输入的字符串长度：
	int len = strlen(str); //记得包含头文件<string.h>
	
	//创建左右指针：
	char* left = str; //左指针
	char* right = str + len -1; //右指针

	//使用 while循环 配合 左右指针 进行字符串逆序：
	while (left < right)
	//两指针中间还有值就继续逆序
	{
		//使用一个临时变量进行两个元素的逆序
		char tmp = *left; //使用 解引用符号* 获取指针内容
		*left = *right;
		*right = tmp;
		//逆序完一次后就调整一次指针位置
		left++;
		right--;
	}

	//进行打印：
	printf("%s\n", str);

	return 0;
}

Realize the picture:

                    

Final code and implementation effect

Final code:

#include <stdio.h>
#include <string.h>
int main()
{
	//创建 字符数组str :
	char str[10001] = { 0 };

	//输入字符串：
	gets(str); //输入数组数据，gets可以把空格也读入
	
	//求输入的字符串长度：
	int len = strlen(str); //记得包含头文件<string.h>
	
	//创建左右指针：
	char* left = str; //左指针
	char* right = str + len -1; //右指针

	//使用 while循环 配合 左右指针 进行字符串逆序：
	while (left < right)
	//两指针中间还有值就继续逆序
	{
		//使用一个临时变量进行两个元素的逆序
		char tmp = *left; //使用 解引用符号* 获取指针内容
		*left = *right;
		*right = tmp;
		//逆序完一次后就调整一次指针位置
		left++;
		right--;
	}

	//进行打印：
	printf("%s\n", str);

	return 0;
}

Realize the effect: