Question

Write a C program that takes two sets of characters entered by the user and merge them character by character.

Enter the first set of characters: dfn h ate
Enter the second set of characters: eedtecsl
Output: defend the castle

Your program should include the following function:

void merge(char *s3, char *s1, char *s2);

The function expects s3 to point to a string containing a string that combines s1 and s2 letter by letter. The first set might be longer or shorter than the second set. The characters in s1 or s2 left after merging should be appended to the resulting string s3.

1) Assume each input is no longer than 1000 characters.

2) The merge function should use pointer arithmetic (instead of array subscripting). In other words, eliminate the loop index variables and all use of the [] operator in the function.

3) To read a line of text, use the read_line function (below)

int read_line(char *str, int n)

{

     int ch, i = 0;

     while ((ch = getchar()) != '\n')

     { if (i < n)

        { *str++= ch;

           i++;

         }

     }

     *str = '\0';   /* terminates string */

     return i;        /* number of characters stored */

Thank you very much in advance!

Answer 1

#include "stdio.h"
int read_lint(char* ,int);                   // declarte the function to read line
void merge(char*,char*,char*);               // declate the function to merge
int main(void) {
int n=1000;                               // set max characters n = 1000
char a1[n];                               // declarate arrays a1,a2,a3;
char a2[n];
char a3[n+n];
char *str1=a1;                           // set pointers to arrays s1,s2,s3
char *str2=a2;
char *str3=a3;
merge(str3,str1,str2);                   // call the merge function.
printf("%s\n",str3);                   // print merged string
return 0;
}
void merge(char *str3,char *str1,char *str2){
   int l1,l2,l3,min,i,j,n=1000;                       // declare variables
printf("Enter the first set of characters:");
l1 = read_line(str1,n);                               // get input string
printf("Enter the second set of characters:");
l2 = read_line(str2,n);                               // get input string
min = l1>l2?l2:l1;                                   // calculate the min length of two strings
for(i=0,j=0;i<min;i++){                               // until min length
   *(str3+ j++) = *(str1+i);                       // add character to str3 from str1
   *(str3+ j++) = *(str2+i);                       // add character to str3 from str2
}
while(l1>i){                                       // if str1 has more characters add it to str3
   *(str3 + j++) = *(str1+ i++);
}
while(l2>i){                                       // if str2 has more characters add it to str3
   *(str3 + j++) = *(str2+ i++);
}
}

int read_line(char *str, int n)
{
int ch, i = 0;
while ((ch = getchar()) != '\n')
{ if (i < n)
{ *str++= ch;
i++;
}
}
*str = '\0'; /* terminates string */
return i; /* number of characters stored */
}

/* sample output

Enter the first set of characters: dfn h ate
Enter the second set of characters: eedtecsl
defend the castle

*/