59 lines
989 B
C
59 lines
989 B
C
#include <stdio.h>
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#include <stdlib.h>
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#include <time.h>
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int is_palindrome(int num, int base);
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int main(int argc, char **argv)
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{
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int i, j, max = 0, num;
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double elapsed;
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struct timespec start, end;
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clock_gettime(CLOCK_MONOTONIC, &start);
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for(i = 999; i >= 100; i--)
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{
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for(j = i; j >= 100; j--)
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{
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num = i * j;
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if(num > max && is_palindrome(num, 10))
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{
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max = num;
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}
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}
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}
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clock_gettime(CLOCK_MONOTONIC, &end);
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elapsed = (end.tv_sec - start.tv_sec) + (double)(end.tv_nsec - start.tv_nsec) / 1000000000;
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printf("Project Euler, Problem 4\n");
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printf("Answer: %d \n", max);
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printf("Elapsed time: %.9lf seconds\n", elapsed);
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return 0;
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}
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int is_palindrome(int num, int base)
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{
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int reverse = 0, tmp;
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tmp = num;
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while(tmp > 0)
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{
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reverse *= base;
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reverse += tmp % base;
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tmp /= base;
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}
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if(num == reverse)
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{
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return 1;
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}
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return 0;
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}
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