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Using while loops to find palindromes?

Using while loops to find palindromes?, The assignment requires that the output shows that an input number is

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arizonaguy1990	4 Oct, 2008 - 04:52 PM Post #1
New D.I.C Head Joined: 4 Oct, 2008 Posts: 1	The code can only have while loops, though here i have included a function for powers before main, only because i forgot how to use the math library and using power functions (i believe its only double). If i can somehow eliminate the need for this beginning function, and fix the while loops to where the program recognizes all positive integers as palindromes, it would make it run smoother and with more accuracy. * Oh and it has to be in the C language* Here is the assignment: -Write a program to check if a given positive integer is a palindrome or not. A palindrome number is one that reads the same forward and backwards. Your program MUST use while statements only. Call this program palindrome-number.c. Example: 12321 is a palindrome number. 123 is not. CODE #include <stdio.h> int power(int a, int b) { int i = 0; int result = a; for (i = 0; i < b - 1; i++) { result = result * a; } return result; } main () { int init; int x; int y; int first; int last; int p; printf("Give me a positive integer:\n"); scanf("%d", &x); while (x < 0) { printf("Not a positive integer, try again:\n"); scanf("%d",&x); } init = x; while (x > 9) { p=1; while (x / power(10,p) > 9) { p++; } first = x / power(10,p); last = x%10; x = x - power(10, p); x = x / 10; while (first != last) { printf("%d is not a palindrome.", init); break; } } printf("%d is a palindrome.", init); } This post has been edited by arizonaguy1990: 4 Oct, 2008 - 08:19 PM
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Martyr2

4 Oct, 2008 - 08:10 PM

Post #2

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My Contributions

Well here is are two ways you can do it. The first is treating it as a string and the second is using the math.

cpp


#include <iostream>
using namespace std;

bool isPalindrome(int number);

int main() {
	char text[20];

	cout << "Enter a string: ";
	cin >> text;

	int start = 0;
	int end = strlen(text) - 1;

	bool palindrome = true;

	// While loop comparing characters at start and end
	while (start < end) {
		if (text[start] != text[end]) {
			palindrome = false;
			break;
		}

		start++;
		end--;
	}

	// Check the flag to see if palindrome was found
	if (palindrome == false) {
		cout << "Not a palindrome" << endl;
	}
	else { cout << "Palindrome" << endl; }

	return 0;
}

cpp


#include <iostream>
using namespace std;

bool isPalindrome(int number);

int main() {
	int anumber;

	cout << "Enter an integer: ";
	cin >> anumber;

	// Call our function to test if it is a palindrome
	if (isPalindrome(anumber)) {
		cout << "Palindrome" << endl;
	}
	else { cout << "Not a palindrome" << endl; }


	return 0;
}

// Use a while loop to test for a palindrome. Returns true or false.
bool isPalindrome(int number) {  
  
     int rev=0,rem;  
	
     int num = number;
     while (num > 0) 
     {  
         rem=num%10;  
         rev=rev*10+rem;  
         num /= 10;
     }  

     if (rev == number) { return true; }  

     return false;  
}

So either one will work. It is up to you on how you want to do it. You can use these as a guide to figure out some ways of doing it. Enjoy!

"At DIC we be palindrome tossing code ninjas... here catch skyhawk! Damn man, you dropped it. You suck!"