Daily question - inverted string

  The topic comes from niuke.com

describe

Invert the words of a sentence , Punctuation is not inverted . such as I like beijing. After passing through the function, it becomes ：beijing. like I

Input description :

 Each test input contains 1 Test cases ： I like beijing.  The length of the input case shall not exceed 100

Output description :

 Output the inverted string in turn , Split by space 

Example 1

Input ：

I like beijing.

Output ：

beijing. like I

Their thinking ：

First flip the whole string , Then flip each word part of the flipped string twice .

Tips ： The end of the string is marked '\0';  When we traverse the string and encounter spaces , We can interpret it as encountering words .

for example ：I Like beijing.

First step , The whole string is inverted , obtain ：.gnijieb ekil I

The second step , Invert every word in the string , obtain ：biejing. like I

Bloggers bring you two ways , One is common practice , Suitable for beginners to understand programming , One involves pointers , General functions are used to flip .

Common practice ：

#include<stdio.h>
#include<string.h>
void FStr(char *Str, int n)
{
	int i = n - 1;
    // Defines an array of character types a, Used to store flipped data 
	char a[150] = { 0 };
	while (*Str != '\0')
	{
		a[i]=*Str;
		++Str;
		--i;
	}
    // The string that flips the whole , Copy to Str Array , Change the original data 
     strcpy(Str,a);
	/*i = 0;
	while (i<n)
	{
		Str[i] = a[i];
		++i;
	}*/
   
	for (i=0;i<n-1;++i)
	{
		int j = i;
        // Traverse to determine the number of characters before the space , It can be understood as the word 
		while (a[j] != '\0' && a[j] != ' ')
		{
			++j;
		}
		int index = i;
        // Flip the character before the space , Give to the Str Array 
		while (j > index)
		{
			Str[i] = a[j-1];
			--j;
			++i;
		}
	}
    // Flip to finish printing Str
	printf("%s\n",Str);
}
int main()
{
	char Str[150]= {0};
    // Input string 
    gets(Str);
	// The inverse 
	FStr(Str,strlen(Str));
	return 0;
}

Advanced approach ：

#include <stdio.h>
#include <string.h>
 
void FStr(char* begin, char* end)// Flip strings 
{
    while(begin <=end)
    {
        char tmp =* begin;
       * begin = *end;
        *end= tmp;
        ++begin;
        --end;
    }
}
 
int main()
{
    char str[100] ={0};
    gets(str);
    // Record the number of characters in the string 
    int n = strlen(str);
    // Flip the string as a whole 
   FStr(str, str+n-1);//str+n-1, amount to &str[n-1]
    char* start = str;
    // Flip each word in the string 
    while(*start)
    {
        char* end = start;
        // Traverse to confirm the number of characters before the space 
        while(*end != ' ' && *end!='\0')// Look for spaces or '\0'
        {
            end++;
        }
        // Flip space 、 End mark '\0' The first character 
        FStr(start, end - 1);
        if(*end == ' ')// Skipping spaces does not participate in flipping 
        {
            start = end + 1;
        }
        else
        {
            start = end;
        }
     }
    // Print 
    printf("%s",str);
    return 0;
}

Interested friends can click on the link to try to use the blogger's method , Or do it in your own way .

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