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#include <stdio.h>
 
int main()
{
    char arr[100] = { 0 };
    gets(arr);//注意没有使用scanf,因为scanfWhen a space is encountered, it stops accepting input
 
    printf("%s\n",arr);
 
    return 0;
}

2、Invert each word

这其中需要注意几点：

1.How the whole statement ends the loop

2.The start and end positions of each word

3.内部如何实现

4. 判断语句结束,Thereby stopping the reverse order

How the statement ends the loop：

	char* t = arr;//Put the address of the first element of the character array into a pointer variablet中
	while (*t!='\0') {  
//判断当*t指向'\0’时循环结束.
}

The start and end positions of each word ：

char* t = arr;//Put the address of the first element of the character array into a pointer variablet中
	while (*t!='\0') {  //判断当*t指向'\0’时循环结束.
		char* start = t;
		char* end = t;
		  //When the end pointer points to a space,并且指向‘\0’循环结束.
		while (*end != ' '&&*end != '\0') {
			end++;
		}

内部怎么实现：

We need to define another function ourselvesreverse,Used to implement the exchange of strings

void reverse(char* left, char* right) {
	while (left < right) {//Only if the address on the left is less than the address on the right,才交换,The middle ones do not need to be exchanged
		char tmp = *right;
		*right = *left;
		*left = tmp;
		left++;
		right--;
	}
}

再调用这个函数：

int main() {
	char arr[100] = { 0 };
	gets(arr); //输入字符数组
	char* t = arr;//Put the address of the first element of the character array into a pointer variablet中
	while (*t!='\0') {  //判断当*t指向'\0’时循环结束.
		char* start = t;
		char* end = t;
		  //When the end pointer points to a space,并且指向‘\0’循环结束.
		while (*end != ' '&&*end != '\0') {
			end++;
		}
		reverse(start, end - 1);
	}

How to judge the end of the sentence,To stop the reverse order

if (*end != '\0')//Check if the end of the string is reached
			t = end + 1;//让指针p指向下一个单词,Let the loop go to the next word
		else
			t = end;

3、将字符串逆置

This is used to calculate the length of the stringstrlen函数,

int len = strlen(arr);

再调用reverse函数:

reverse(arr, arr + len - 1);

四、代码总结

void reverse(char* left, char* right) {
	while (left < right) {
		char tmp = *right;
		*right = *left;
		*left = tmp;
		left++;
		right--;
	}
}
int main() {
	char arr[100] = { 0 };
	gets(arr); //输入字符数组
	char* t = arr;//Put the address of the first element of the character array into a pointer variablet中
	while (*t!='\0') {  //判断当*t指向'\0’时循环结束.
		char* start = t;
		char* end = t;
		  //When the end pointer points to a space,并且指向‘\0’循环结束.
		while (*end != ' '&&*end != '\0') {
			end++;
		}
		reverse(start, end - 1);
		if (*end != '\0')//Check if the end of the string is reached
			t = end + 1;//让指针p指向下一个单词,Let the loop go to the next word
		else
			t = end;
	}
	int len = strlen(arr);
	reverse(arr, arr + len - 1);
	printf("%s\n", arr);
	return 0;
}

五、The second method inverts the string

The idea of method 2 is to use it firstt指向字符串的末尾,然后往前走,找到空格时,printf一下,以%s格式,这样打印只需要给字符串的首地址,它打印到\0停下.我们打印完一个单词后,把t的位置变成\0,然后继续往前走,直到数组开始位置.
t指针开始指向字符串最后一个字符,然后往前遍历,直到空格或者t到了最开始的字符位置,这里分两种情况,到空格位置,要Change the space position to \0,打印cur+1位置,到首字符,打印cur位置.
其中需要注意一点,我们Change the space position to 了\0,所以在第一种情况需要打印的时候在加个空格

代码如下：

int main()
{
    char arr[100] = { 0 };
    gets(arr);
    char* t = arr + strlen(arr) - 1;  //将tPointer to the last character of the string
    while (t > arr)    //当tThe address of the pointer is greater thanarrThe first element address starts the loop
    {
        while (*t != ' ' && t > arr)  //当t不为空格时,tThe pointer loops forward
        {
            t--;
        }

        if (t == arr)
        {
            printf("%s", t);
        }
        else //到空格,打印t+1位置
        {
            printf("%s ", t + 1);
            *t = '\0';   //Change the space position to ‘\0’
        }
    }
    return 0;
}