Problems with Palindromes in C
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06-12-2019 - |
سؤال
I've written some code in C to try adn find whether or not a number is a Palindrome. The rule is that two 3 digit numbers have to be multiplied together and you have to find the highest palindrome. the answer should be 906609 but my code only gets to 580085.
the code:
#include <stdio.h>
#include <stdlib.h>
/* Intialise */
void CalcPalin();
int CheckPalin(int number);
/* Functions */
void CalcPalin()
{
int result = 0;
int palin = 0;
int FNumber = 0;
int FNumber2 = 0;
int number = 99;
int number2 = 100;
while(number2 < 1000)
{
number += 1;
/*times together - calc result*/
result = number * number2;
if(CheckPalin(result) == 1)
{
palin = result;
FNumber = number;
FNumber2 = number2;
}
if(number == 999)
{
number = 99;
number2 += 1;
}
}
printf(" Result = %d, by Multiplying [%d] and [%d]", palin, FNumber, FNumber2 );
}
int CheckPalin(int number)
{
int checknum, checknum2 = 0;
checknum = number;
while(checknum)
{
checknum2 = checknum2 * 10 + checknum % 10;
checknum /= 10;
}
if( number == checknum2)
return 1;
else
return 0;
}
int main( void)
{
CalcPalin();
return EXIT_SUCCESS;
}
Im pretty sure its a stupid answer and im over looking something simple but i cant seem to find it. Any help would be great
المحلول
You have not tested whether the current result is higher than one old result. Add this check.
// test new result is higher than old palin before setting this as palin
if(CheckPalin(result) == 1 && palin < result)
نصائح أخرى
Your algorithm print :
Result = 580085, by Multiplying [583] and [995]
It seems that you should find a way to increment more the 1st number. There is many possibility between 583 and 999 in order to get to 906609.
EDIT : In fact, you are looking for 993 * 913 = 906609.
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