Reversing a string in c with recursion

Question

I have written code to reverse a string in c... it works fine but I can\'t return the reversed string in the main() function.

#include

        

Answer 1

a little change in Emre Can Kucukoglu's answer . . . we can eliminate strncat_s

void revstr_rec(char *sstr, char *dstr, int len)
{
    int i = 0;
    if((! *sstr) || (! len) )
        return;

    revstr_rec(sstr + 1, dstr, len - 1);
    dstr[len - 1] = *sstr;

    return;
}

int main()
{
    char *sstr = NULL;
    char *dstr = NULL;

    sstr = malloc(16);
    if(! sstr)  {
        printf("no memory . . .\n");
        return 0;
    }
    strcpy(sstr, "hello world !");
    printf("sstr: %s\n", sstr);

    dstr = malloc(16);
    if(! dstr)  {
        printf("no memory . . .\n");
        return 0;
    }

    revstr_rec(sstr, dstr, strlen(sstr));
    printf("dstr(recursive): %s\n", dstr);

    free(sstr);
    free(dstr);

    return 0;
}

Answer 2

This code is not executable :( You define int reverse but reverse function doesnt return any value

instead use this (using void):

#include<stdio.h>

main()
{
  char a[17]="abcdefg";
  reverse(a);
  printf("\n");
  system("PAUSE");
}
void reverse(char *a)
{
   if(*a!='\0')
   {   
     reverse(a+1);
   }
   printf("%c",*a);
}        

Answer 3

#include<stdio.h>
void reverse(char *a);
main()
{
  char a[17]="abcdefg";
  reverse(a);
  printf("\n");
  system("PAUSE");
}
void reverse(char *a)
{
   if(*a!='\0')
   {   
     reverse(a+1);
   }
   printf("%c",*a);
}  

Answer 4

void palindromo(char *s)
{
    if(s[0] != '\0'){
        palindromo(s+1);
        printf("%c", s[0]);
    }
}

This is a small recursive function who print the string inverted.

Answer 5

#include<stdio.h>
#include<string.h>
void rev(char *);

int main()
{
    char s[]="Hello";
    printf("\n%s",s);
    rev(s);
    printf("\n%s",s);
    return 0;
}

void rev(char *s)
{
    static int i=0;
    static int j=0;
    if(j==0)                   //since static variable can be intitialized 
    {                          //only with a constant literal,to store 
        j=strlen(s)-1;         //length-1 in 1st function call, we can use 
    }                          //this trick.(condition satisfied only in 1st 
                               //function call)
    if(i<j)
    {
        char temp;
        temp=s[i];
        s[i]=s[j];             //Analogous to for(i=0,j=l-1;i<j;i++,j--)
        s[j]=temp;             //                { //swap code }
        i++;
        j--;
        rev(s);           
    }
}