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Print substring of a given string without using any string function and loop in C
  • Difficulty Level : Easy
  • Last Updated : 14 Jul, 2017

Write a function mysubstr() in C that doesn’t use any string function, doesn’t use any loop and prints substring of a string. The function should not modify contents of string and should not use a temporary char array or string.

For example mysubstr(“geeksforgeeks”, 1, 3) should print “eek” i.e., the substring between indexes 1 and 3.

One solution is to use recursion. Thanks to Gopi and oggy for suggesting this solution.




#include<stdio.h>
  
// This function prints substring of str[] between low and
// high indexes (both inclusive).  
void mysubstr(char str[], int low, int high)
{
    if (low<=high)
    {
        printf("%c", str[low]);
        mysubstr(str, low+1, high);
    }
}
  
int main ()
{
    char str[] = "geeksforgeeks";
    mysubstr(str, 1, 3);
    return 0;
}

Output:

eek

How to do it if recursions is also not allowed?
We can always use pointer arithmetic to change the beginning part. For example (str + i) gives us address of i’th character. To limit the ending, we can use width specifier in printf which can be passed as an argument when * is used in format string.




#include <stdio.h>
  
// This function prints substring of str[] between low and
// high indexes (both inclusive).  
void mysubstr(char str[], int low, int high)
{
    printf("%.*s", high-low+1, (str+low));
}
  
int main ()
{
    char str[] = "geeksforgeeks";
    mysubstr(str, 1, 3);
    return 0;
}

Output:

eek

This article is contributed by Rahul Jain. Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above

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