Chapter 15: Strings.md

[Chapter 15: Strings] Solutions

[A]

(a)
    A
    A

(b)
        t organised! learn C!!
        Get organised! learn C!!
        Get organised! learn C!!
        t

(c) 

N N
N N
o o
o o


t t
t t
w w
w w
o o
o o


v v
v v
i i
i i
r r
r r
u u
u u
s s
s s
e e
e e
s s
s s


w w
w w
o o
o o
r r
r r
k k
k k


s s
s s
i i
i i
m m
m m
i i
i i
l l
l l
a a
a a
r r
r r
l l
l l
y y
y y

(d) 
    
    Garbage or error, that t is not initialized.
(e)

Hello[garbage characters because NULL character is missing]
Hello

(f)
Morning

(g) e

(h) 1 2 4

[B]

(a) 

Error: As the str3 is declared but not defined, so it is only
void pointer, so without allocating memory to it, we cannot
store anything to it.

(b) No Error

(c) Error: In arr++ statement. As you can see that arr[8] is initilized
    at the time of declaration. So in that case we cannot assign anything 
    to arr, and statement arr++ is execute as arr = arr + 1, which is 
illegal.

[C]

(a) string,character

(b) NULL,'\0'

(c) 9 characters, and 10th character space is for \0 character.

(d) contiguous.

[D]

(a)

 gets() is more appropriate for reading a multi-word string.

(b)

    str1 : Alice
    str2 : in
    str3 : wonder
    str4 : land

(c)

#include<stdio.h>
#include<conio.h>
#include<string.h>
int main()
{
char sen[100];
int i;
printf("Enter your sentence. (Less than 100 chracters)\n\n");
gets_s(sen);
printf("After how muany characters you want to extract the line : ");
scanf("%d", &i);
i--;
if (i<0)
	i = 0;
printf("%s\t", &sen[i]);
_getch();
return 0;
}

(d)

#include<stdio.h>
#include<conio.h>
int main()
{
char str[100];
int i, num, fin = 0;
printf("Enter a string of numbers : ");
gets_s(str);
for (i = 0; str[i] != '\0'; i++)/*Run until string is not terminated.*/
{
	num = str[i] - 48;/*Converting the character number into integer number.*/
	fin = fin * 10 + num;/*Combining the individual numbers to form a single integers*/
}
printf("\nNumber : %d", fin);
_getch();
return 0;
}

(e)

#include<stdio.h>
#include<conio.h>
#include<string.h>
int main()
{
char x[50] = "a", z[50];
char y[50] = "b";
int i;
for (i = 0; i <= 5; i++)
{
	printf("%s\t", x);//printing x
	strcpy(z, x);/*copying x into z*/
	strcpy(x, y);/*copying y into x*/
	strcat(y, z);/*adding (concatinating) z in y*/
}
_getch();
return 0;
}

(f)

#include<stdio.h>
#include<conio.h>
int main()
{
char isbn[15];
int i, sum = 0;
printf("\nEnter 10 digit ISBN number : ");
gets_s(isbn);
for (i = 0; i <= 9; i++)
{
	isbn[i] -= 48;/*Converting characters into numerals*/
	sum = sum + ((i + 1)*isbn[i]);/*checking the condition of the ISBN validity*/
}
if (sum % 11)/*If not divisble by 11*/
	puts("\nISBN number is wrong.");
else
	puts("\nISBN number is valid.");
_getch();
return 0;
}

(g)

#include<stdio.h>
#include<conio.h>
int main()
{
char num[20];
int i, sum = 0;
printf("\nEnter the 16 digit credit card number : ");
scanf("%s", num);

for (i = 0; i <= 15; i++)//Traversing all numbers
{
num[i] -= 48;//converting each character in numeral
if ((i % 2))//if the number is on right so it will directly get summed
	sum = sum + num[i];
else//if number is on left, so it will first get doubled
{
num[i] *= 2;
if (num[i] >= 10)//if number is greater then or equal to 10 so it will subtracted from 9
num[i] -= 9;
sum = sum + num[i];	//summing number
}
}
if (!(sum % 10))//if sum is divisble by 10 so number is valid
	printf("\nNumber is valid.");
else
	printf("\nNumber is not valid.");
_getch();
return 0;

}