Question

Write a function to find the last occurrence of a string within another string. The function should use the prototype below. Use pointer arithmetic when traversing the strings. (C Language)

char * search_string(const char * str, const char * substr);

Answer 1

Source Code

#include <stdio.h> 
#include <string.h> 

// Function to reverse the string 
// using pointers 
void reverseString(char* str) 
{ 
        int l, i; 
        char *begin_ptr, *end_ptr, ch; 

        // Get the length of the string 
        l = strlen(str); 

        // Set the begin_ptr and end_ptr 
        // initially to start of string 
        begin_ptr = str; 
        end_ptr = str; 

        // Move the end_ptr to the last character 
        for (i = 0; i < l - 1; i++) 
                end_ptr++; 

        // Swap the char from start and end 
        // index using begin_ptr and end_ptr 
        for (i = 0; i < l / 2; i++) { 

                // swap character 
                ch = *end_ptr; 
                *end_ptr = *begin_ptr; 
                *begin_ptr = ch; 

                // update pointers positions 
                begin_ptr++; 
                end_ptr--; 
        } 
} 

// Driver code 
int main() 
{ 

        // Get the string 
        char str[100] = "GeeksForGeeks"; 
        printf("Enter a string: %s\n", str); 

        // Reverse the string 
        reverseString(str); 

        // Print the result 
        printf("Reverse of the string: %s\n", str); 

        return 0; 
} 

The Output