在C ++

Question

我不知道如何递归地运行它。 我尝试递归编码Palindrome函数。我明白我该怎么做：

1       => single digit, therefore yes
--------
12      => 1 != 2, therefore no
--------
121     => 1 == 1, therefore yes
 2      => single digit, therefore yes
--------
1234421 => 1 == 1, therefore yes
 23442  => 2 == 2, therefore yes
  344   => 3 != 4, therefore no

然而，我有一个问题。它没有递归地工作。我需要帮助。 我错过了什么吗？

// Check if a positive integer is a Palindrome
#include <iostream>
using namespace std;

bool isPalindrome(int number, int factor);

int main()
{
    int number; // a positive integer
    cout << "Enter a positive integer: ";
    cin >> number;

    // puts 10^(numDigits-1) (i.e., the smallest numDigits-digit positive integer) into factor
    int temp = number;
    int factor = 1; // power of ten
    while (temp > 9)
    {
        temp /= 10;
        factor *= 10;
    }

    // print whether the number is a palindrome
    if (isPalindrome(number, factor))
        cout << endl << number << " is a palindrome." << endl << endl;
    else
        cout << endl << number << " is not a palindrome." << endl << endl;

    system("pause");
}

bool isPalindrome(int number, int factor){
    int checkFirst, checkSecond, temp;

    if (number / 10 > 0){
        checkFirst = number / factor;
        checkSecond = number % 10;
        if (checkFirst == checkSecond){
            temp = number%factor;
            number = temp;
            isPalindrome(number / 10, factor / 10);
        }
        else
        {
            return false;
        }
    }
    else
    {
        return true;
    }
}

Answer 1

两件事。

递归调用时不使用isPalindrome()的返回值。将其添加为return语句。

return isPalindrome(number / 10, factor / 10);

每次检查两位数时，系数也减少100。因此，将factor除以100。

return isPalindrome(number / 10, factor / 100);

Answer 2

非常感谢!!

// Check if a positive integer is a Palindrome
#include <iostream>
using namespace std;

bool isPalindrome(int number, int factor);

int main()
{
    int number; // a positive integer
    cout << "Enter a positive integer: ";
    cin >> number;

    // puts 10^(numDigits-1) (i.e., the smallest numDigits-digit positive integer) into factor
    int temp = number;
    int factor = 1; // power of ten
    while (temp > 9)
    {
        temp /= 10;
        factor *= 10;
    }

    // print whether the number is a palindrome
    if (isPalindrome(number, factor))
        cout << endl << number << " is a palindrome." << endl << endl;
    else
        cout << endl << number << " is not a palindrome." << endl << endl;

    system("pause");
}
bool isPalindrome(int number, int factor){
    int checkFirst, checkSecond, temp;
    if (number / 10 > 0){
        checkFirst = number / factor;
        checkSecond = number % 10;
        if (checkFirst == checkSecond){
            temp = number%factor;
            number = temp;
            return isPalindrome(number / 10, factor / 100);
        }
        else
        {
            return false;
        }
    }
    else
    {
        return true;
    }
}