63 lines
1.7 KiB
C
63 lines
1.7 KiB
C
#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <openssl/md5.h>
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int main() {
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size_t PUZZLE_SIZE = 8; //puzzle input is 8 characters with no ending newline character
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//load input string
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FILE *file = fopen("input", "r");
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if (file == NULL) {
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perror("main: error opening file.");
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return -1;
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}
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char input[256];
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while (fgets(input, sizeof(input), file));
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if (strlen(input) != PUZZLE_SIZE) {
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perror("main: error reading file.");
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return -1;
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}
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printf("puzzle input: %s\n", input);
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//initialize MD5 context
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//note: ignore gcc's warnings that MD5 is depreciated
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MD5_CTX md5_context;
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uint8_t md5_hash[MD5_DIGEST_LENGTH];
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char md5_string[MD5_DIGEST_LENGTH * 2 + 1]; //32 hexadecimal digits
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//each byte needs two characters in hex, plus one for '\0'
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char *md5_string_ptr = md5_string;
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int32_t chars_written;
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int32_t available_space;
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int32_t count = -1; //initialize count at -1 so that the first count++ sets it to 0
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while (strncmp(md5_string, "000000", 6) != 0) {
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count++;
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chars_written = snprintf(input + PUZZLE_SIZE, sizeof(input) - strlen(input), "%i", count);
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available_space = sizeof(input) - strlen(input);
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if (chars_written >= available_space) {
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perror("main: buffer overflow.");
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return -1;
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}
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//initialize MD5 context
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MD5_Init(&md5_context);
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//update context with input (+ count) data
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MD5_Update(&md5_context, input, strlen(input));
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//finalize MD5 hash
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MD5_Final(md5_hash, &md5_context);
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for (int i = 0; i < MD5_DIGEST_LENGTH; i++) {
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md5_string_ptr += sprintf(md5_string_ptr, "%02x", md5_hash[i]);
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}
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md5_string_ptr = md5_string; //reset pointer
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}
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printf("count %i: %s\n", count, md5_string);
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return 0;
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}
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