Question

1. DOES A DIGIT APPEAR IN AN INTEGER, Write a recursive function appears(n,i) that returns true if the digit i appears in the positive (base 10) integer n, false if it does not in c++. ex.

Enter a positive integer: 54321
          Enter a digit: 7
          The digit 7 does NOT appear in the integer 54321.

2. IS AN INPUT STRING A PALINDROME? A palindrome is a string in which the letters are the same in both directions, disregarding capitalization and non-letter characters. Write a program that reads a sequence of characters and calls a recursive Boolean function to determine if the letters in the string form a palindrome in c++. example:

csh> pal
      Enter a line that might be a palindrome:
      Madam I'm Adam.
      This string IS a palindrome.

Answer 1

1)

#include <bits/stdc++.h>

using namespace std;

bool appears(int n, int i)

{

// Base case

if(n < 10)

{

return (n == i);

}

// If last digit is i return true

if(n%10 == i)

return true;

// Else recur for n/10

return appears(n/10, i);

}

int main()

{

cout << "3 appears in 1234: " << appears(1234, 3) << " 6 appears in 1234: " << appears(1234, 6);

return 0;

}

Output :

2)

#include <bits/stdc++.h>

using namespace std;

bool palindrome(char str[], int s, int e)

{

// Base case

if(s == e || s + 1 == e)

return true;

// If start is special character then increment s

while((str[s] < 'a' || str[s] > 'z') && (str[s] < 'A' || str[s] > 'Z'))

s++;

// If end is special character then decrement e

while((str[e - 1] < 'a' || str[e - 1] > 'z') && (str[e - 1] < 'A' || str[e - 1] > 'Z'))

e--;

// If start and last are unequal then return false

if(tolower(str[s]) != tolower(str[e - 1]))

return false;

// Otherwise recur

return palindrome(str, s + 1, e - 1);

}

int main()

{

char str[100];

cout << "Enter the string ";

cin >> str;

if(palindrome(str, 0, strlen(str)))

cout << "Palindrome ";

else

cout << "Not Palindrome ";

return 0;

}

Output:

$Enter the string Aba Palindrome PS C:\Users Aashutosh Khandelwal\Documents VSC\Chegg ./a.exe Enter the string abcba Palindrome$

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