what is the problem of this code and why this code always run the "non-palindrome" even though i checked algorithm several times | Sololearn: Learn to code for FREE!

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what is the problem of this code and why this code always run the "non-palindrome" even though i checked algorithm several times

#include <iostream> bool isPalindrome(int x){ int a,sum=0; while(x>0){ a=x%10; sum=sum*10+a; x=x/10; } } int main() { int x; int sum; std::cin>>x; if(isPalindrome(x)) {std::cout<<sum<<"is a palindrome";} else {std::cout<<sum<<"is not a palindrome";} }

9/23/2021 11:36:30 PM

Nariman Tajari

15 Answers

New Answer

+4

Possible problems are: 1) isPalindrome() returns no boolean, 2) it doesn't determine whether x is palindrome or not. Cheer!

+3

Hi Martin Taylor I agree that a string problem is easier to resolve, but I find this approach quite interesting.

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You haven't compared your input value and sum ......and then u haven't returned any Boolean value too... This code will do... #include <iostream> bool isPalindrome(int p){ int a,sum=0,c=p; while(c>0){ a=c%10; sum=sum*10+a; c=c/10; } if(p==sum) return true; else return false; } int main() { int x; std::cin>>x; if(isPalindrome(x)) {std::cout<<x<<" is a palindrome";} else {std::cout<<x<<" is not a palindrome";} }

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Why don't people use the search bar? Why do people think this is a math problem? A palindrome is a number word or phrase that reads the same forwards or backwards. It is therefore a string comparison problem not a mathematical one. https://www.sololearn.com/Discuss/2888911 https://www.sololearn.com/Discuss/2888114 https://www.sololearn.com/Discuss/2887297 https://www.sololearn.com/Discuss/2885073 That's just this week.

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Yep, his code is very close. I hope he make it his way……

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Rik Wittkopp i have run the adjusted version which you recommend but the problem is why rhe out put is always non palindrom and doesnt give a right conditional , for example when you enter 252 it says it is non palindrome and its wrong.

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#include <iostream> bool isPalindrome(int x){ int a,sum=0; while(x>0){ a=x%10; sum=sum*10+a; x=x/10; } return sum; if (sum==x) return true; else return false; } int main() { int x; //int sum; std::cout<<isPalindrome(887); std::cin>>x; if(isPalindrome(x)) {std::cout<<x<<"is a palindrome";} else {std::cout<<x<<"is not a palindrome";} } But why now it returns always true and the conditionals doesnt work as it should? Rik Wittkopp Shizuku Martin Taylor

+1

You have an excess return statement. It returns always true and quits the program before if-else statement. Note that any non-zero value will be considered true!

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But Shizuku is there a way to give the problem a function which qould have have the right boolean form? You know how would i write this section?

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Just ONE malicious line, bro. And mind you, inside main() should not have been altered. Maybe original main() goes like: int main() { int n; cin >>n; if(isPalindrome(n)) { cout <<n<<" is a palindrome"; } else { cout << n<<" is NOT a palindrome"; } return 0; } Good luck.

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Nariman Tajari I know that you have received a number of solutions already, but I would like to present a working solution using the concepts of our discussion. #include <iostream> bool isPalindrome(int num){ int a,x,sum=0; x = num; while(x>0){ a=x%10; sum=sum*10+a; x=x/10; } return sum == num; } int main(){ int x; std::cin>>x; if(isPalindrome(x)){ std::cout<<x<<" is a palindrome"; } else { std::cout<<x<<" is not a palindrome"; } }

0

Nariman Tajari There are a number of problems with your code. 1. Your Boolean function does not work. It did not have a return from the function so no result could be produced when the function was called. Also, your variable sum =0, but later you want a value multiplied by sum, which will be 0, 6*0=0. There is another problem within your logic but I am hoping you can resolve that yourself, (meaning I stopped looking for it) 2. in main() you have int sum. You then attempt to get a boolean value from your function, followed by a statement referring to sum, which has not yet been assigned to a value. I have modified your code a bit. Fix the logic within your bool function & it should work Delete the test boolean section when ready

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Nariman Tajari The adjusted code I mentioned. #include <iostream> bool isPalindrome(int x){ int a,sum=0; while(x>0){ a=x%10; sum=sum*10+a; x=x/10; } return sum == x; } int main(){ // testing boolean function std::cout << isPalindrome(262)<<std::endl; int x; //int sum; std::cin>>x; if(isPalindrome(x)){ std::cout<<x<<" is a palindrome"; } else { std::cout<<x<<" is not a palindrome"; } }

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Nariman Tajari I fixed your bool function, which I will attach. I have left all my test notes in place for you to review. The problem was that x was being reduced to 0, while sum was being constructed #include <iostream> bool isPalindrome(int num){ int a,x,sum=0; x = num; std::cout<<x << std::endl; while(x>0){ a=x%10; sum=sum*10+a; x=x/10; //std::cout << a << std::endl; std::cout << sum << std::endl; } std::cout << x << std::endl; return sum == num; } int main(){ // testing boolean function std::cout << isPalindrome(262)<<std::endl; }

0

#include <algorithm> #include <string> #include <cmath> #include <vector> #include <iostream> int lengthValue(int ); bool isPalindrome(int ); int main( ){ std::cout<<std::boolalpha<<isPalindrome(555); return 0; } int lengthValue( int value){ int i=0; while ( value > 0){ value /= 10; ++i; } return i; } bool isPalindrome(int value){ int length=lengthValue(value); std::vector<int> vec, vec2; int i(0); int divide; for (int i=length-1; i >=0 ; --i){ divide = value / (int)std::pow(10,i); value %= (int) std::pow(10,i); vec.push_back(divide); } vec2 = vec; std::reverse(vec2.begin(),vec2.end()); if ( vec == vec2) return true; return false; }