生成回文

Question

最近我写了这个quick'n'dirty代码，它产生如下的回文：

int main() {
    generateEvenPalindromes(1);
}

unsigned long generateEvenPalindromes(int lowerBound) {
    unsigned long palindrome = 0;
    int upperBound = lowerBound * 10;

    for (int i = lowerBound; i < upperBound; i++) {
        palindrome = appendMirroredValueToNum(i, -1);    // -1 means 'no middle digit'
        printf("%lu\n", palindrome);
    }
    return generateOddPalindromes(lowerBound);
}

unsigned long generateOddPalindromes(int lowerBound) {
    unsigned long palindrome = 0;
    int upperBound = lowerBound * 10;

    for (int i = lowerBound; i < upperBound; i++) {
        for (int j = 0; j < 10; j++) {
            palindrome = appendMirroredValueToNum(i, j);
            printf("%lu\n", palindrome);
        }
    }
    if (upperBound > 10000) {
        return 0;
    }
    return generateEvenPalindromes(upperBound);
}

unsigned long appendMirroredValueToNum(int num, int middleDigit) {
    //...
    return newNumber;
}

- 它产生一系列 aa 和 aba 回文序列，其中a [1; 99999]，b [0; 9]，即

11
22
...
99
101
111
121
...
217712
218812
219912
...
99999899999
99999999999

- 我正在考虑使用函数 generateEvenPalindromes（）和 generateOddPalindromes（）并将它们合并为一个。如果您认为这是个好主意，请您推荐一个好的方法来实现这个目标吗？