108 lines
1.8 KiB
C
108 lines
1.8 KiB
C
#include <stdio.h>
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#include <stdlib.h>
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#include <time.h>
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int is_pandigital(int value, int n);
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int main(int argc, char **argv)
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{
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int i, j, tmp;
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long int n, max = 0;
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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 = 1; i < 10000; i++)
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{
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n = 0;
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j = 1;
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do
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{
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tmp = i * j;
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n += tmp;
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j++;
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if(n > max && is_pandigital(n, 9))
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{
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max = n;
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}
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if(i * j < 10)
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{
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n *= 10;
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}
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else if(i * j < 100)
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{
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n *= 100;
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}
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else if(i * j < 1000)
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{
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n *= 1000;
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}
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else if(i * j < 10000)
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{
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n *= 10000;
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}
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else if(i * j < 100000)
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{
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n *= 100000;
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}
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}while(n <= 987654321);
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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 38\n");
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printf("Answer: %ld\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_pandigital(int value, int n)
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{
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int *digits;
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int i, digit;
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if((digits = (int *)calloc(n+1, sizeof(int))) == NULL)
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{
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fprintf(stderr, "Error while allocating memory\n");
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exit(1);
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}
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for(i = 0; i < n && value > 0; i++)
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{
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digit = value % 10;
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digits[digit]++;
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value /= 10;
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}
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if(i < n || value > 0)
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{
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free(digits);
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return 0;
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}
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if(digits[0] != 0)
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{
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free(digits);
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return 0;
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}
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for(i = 1; i <= n; i++)
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{
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if(digits[i] != 1)
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{
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free(digits);
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return 0;
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}
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}
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free(digits);
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return 1;
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}
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