Hallo, I would like to wrote a programme that has two bool functions, one for decimal and one for binary. The function is supposed to show whether the given parameter is a palindrome in decimal or binary system or not. Now here is the tricky part. No divisions and multiplications allowed.
Convert it to a string.
Quzah.
Hope is the first step on the road to disappointment.
Convert a number to string. Interesting. I don't really know how I can convert a number to a string. So I have 15, how can I convert it this to a string? I thought they were two separate data types that can't be mixed.
In binary (haven't tested, just an idea):
In decimal:Code:inline bool getbit(unsigned x, unsigned bit) { // gets specified bit starting from 0 return (x & (1 << bit)) != 0; } bool testbin(unsigned x) { // count number of visible digits unsigned n = 0; unsigned tempx = x; do { ++n; tempx >>= 1; } while (tempx > 0) // using previously computed number, test if palindrome for (unsigned i = 0; i < n >> 1; i++) // n >> 1 since n / 2 is not allowed { if (getbit(x, i) != getbit(x, n - i - 1)) return false; } return true; }
depends whether modulo is also allowed.
Thanks but you used division (i < n / 2) and no division is allowed.
You can always implement division and multiplications with shifts. Just horribly inefficient when you have dedicated circuits in your CPU that can do them in hardware.
PS I left a bug in the code.......Code:bool IsPalindrome(int Input) { char szInput[MAX_PATH] = {'0'}; //convert to string _snprintf(szInput, MAX_PATH -1, "%d", Input); //find length int Len = lstrlen(szInput); //for each character for(int i=0;i<Len;i++) { //check to see if corresponding chars match if(szInput[i] != szInput[Len-i]) { //is not palindrome return false; } if(i >= (Len - i) )//more than 1/2 way thru string and each char has matched, so is palindrome { return true; } } return false; }
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I edited it a few seconds before you posted.Originally Posted by Dontgiveup
It is very likely that printf uses division to do the conversion.
