75 lines
1.8 KiB
C
75 lines
1.8 KiB
C
#include <stdio.h>
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#include <stdlib.h>
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#define true 1
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#define false 0
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#define boolean char
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/*
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A palindromic number reads the same both ways. The largest palindrome made from the product of two 2-digit numbers is 9009 = 91 × 99.
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Find the largest palindrome made from the product of two 3-digit numbers.
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https://projecteuler.net/problem=4
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*/
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struct String{
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int length;
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char*str;
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};
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struct String numberToString(int numb) {
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int placeValues=0;
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int tempNumb=numb;
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while (tempNumb>0) {
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tempNumb/=10;
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placeValues++;
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}
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char*finalStr=malloc(placeValues+1);
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tempNumb=numb;
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int marker=placeValues-1;
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while (tempNumb>0) {
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finalStr[marker--]='0'+(tempNumb%10);
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tempNumb/=10;
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}
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struct String str={placeValues,finalStr};
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return str;
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}
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boolean isPalindrome(struct String numb) {
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int offset=0;
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while (offset<numb.length/2) {
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//printf("Compare %c to %c\n",numb.str[offset],numb.str[numb.length-offset-1]);
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if (numb.str[offset]!=numb.str[numb.length-offset-1]) {
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return false;
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}
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offset++;
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}
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return true;
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}
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int main(int argc,char**argv) {
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int numb1=999;
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int numb2=999;
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int maxPal=0;
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//printf("%s : %d",numberToString(numb1*numb2).str,numberToString(numb1*numb2).length);
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for (numb1=999;numb1>0;numb1--) {
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for (numb2=999;numb2>0;numb2--) {
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struct String str = numberToString(numb1*numb2);
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if (isPalindrome(str)) {
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printf("%d is a Palindrome!\n",numb1*numb2);
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if (maxPal<numb1*numb2) {
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maxPal=numb1*numb2;
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printf(" New MAX set to %d\n",maxPal);
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}
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}
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free(str.str);
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}
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}
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printf("\n\nThe maximum palindrome is %d\n",maxPal);
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return 0;
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} |