Question

This program works with strings complete the following functions to allow the program to function properly;

a) Write a C function int string_to_number(char *) that takes a string of decimal digits as an input parameter, and returns the integer value that the string represents. For example, if the char s[] ="256", then string_to_number(s) returns integer 256 (int data type). You are allowed to use strlen(…) function, but not allowed to use atoi and other functions. Ignore the negative sign and overall.

b) Write a C function void reverse(char *s) that takes a string as input, and reverses the order of its characters and stores in the string. For example, if string s is "abcd", after the function call, s becomes "dcba". You are allowed to use strlen(…) function.

c) Implement the above function without using strlen function. Just use pointer notation.

Answer 1

C CODE:

A.

#include
#include
int string_to_decimal(char *a,int n){
   int i,k=0;
   for(i=0;a[i]!='\0';i++){
       //logic for converting string to int
       k=k*10+a[i]-'0';
   }
   return k;
}
int main(){
   int n;
   printf("Enter the length of string\n");
   scanf("%d",&n);
   printf("Enter the string of length %d \n",n);
char s[n];  
   scanf("%s",&s);
   int res=string_to_decimal(s,strlen(s));
   printf("Number changed to int is %d",res);
   //printf("%d",res);
}

SCREENSHOT OF THE CODE AND OUTPUT:

B.

#include
#include

void reverse(char *s){
   int n,low,high;
   n=strlen(s);
   high=n-1;
   char k[50];
   for(low=0;s[low]!='\0';low++){
       k[low]=s[high];//copying into new string
       high--;
   }
   k[low]='\0';
   printf("Reversed string is %s",k);

  
}
int main(){
  
   printf("Enter the string\n");
char s[50];  
   scanf("%s",&s);//taking input
   //calling reverse function
   reverse(s);
  
}

SCREENSHOT OF THE CODE AND OUTPUT:

C.

#include
#include

int fun(char *s)
{
int i = 0;

while( *(s+i) != '\0' )
{
   i++;}

return i;
}
void reverse(char *s)
{
int n, i;
char *low, *high, temp;

n= fun(s);


low = s;
high = s;

for (i = 0; i < n - 1; i++)
{
   high++;}

for (i = 0; i < n/2; i++)
{
temp = *high;//storing anf swapping
*high = *low;
*low= temp;

low++;
high--;
}


}

int main(){
  
   printf("Enter the string\n");
char s[50];  
   scanf("%s",&s);//taking input
   //calling reverse function
   reverse(s);
   printf("Reversed string is %s",s);
}

SCREENSHOT OF THE CODE AND OUTPUT: