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part1.c
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part1.c
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#include <stdio.h>
#include <string.h>
#include <openssl/md5.h>
// solution time: 29:56.78 (mm:ss.ms)
int main() {
// open input.in
FILE *fp = fopen("input.in", "r");
// read input
char hash[100];
fscanf(fp, "%99s\n", hash);
// close input.in
fclose(fp);
int i = 0;
while (1) {
// create a string with the number
char str[100];
sprintf(str, "%d", i);
// create a string with the hash
char hash_str[100];
sprintf(hash_str, "%s%s", hash, str);
// calculate the hash
unsigned char reshash[MD5_DIGEST_LENGTH];
MD5((unsigned char*) hash_str, strlen(hash_str), reshash);
// copy the first 5 bytes of reshash to a new array as hex
char reshash_hex[100];
for (int j = 0; j < 5; j++) {
sprintf(reshash_hex + (j * 2), "%02x", reshash[j]);
}
// check if the first 5 bytes are 0
int j;
for (j = 0; j < 5; j++) {
if (reshash_hex[j] != '0') break;
}
// if it does, break
if (j == 5) break;
// otherwise, increment i
i++;
// for (j = 0; j < MD5_DIGEST_LENGTH; j++) {
// printf("%02x", reshash[j]);
// }
// printf("\n");
}
// print answer
printf("%d\n", i);
return 0;
}