From 3aa641542918765f6ceb039cfa64ff6f58597eb2 Mon Sep 17 00:00:00 2001
From: Marvin Borner
Date: Tue, 30 Nov 2021 21:53:46 +0100
Subject: Hype for tomorrow

---
 2015/04/solve.c | 118 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 118 insertions(+)
 create mode 100644 2015/04/solve.c

(limited to '2015/04/solve.c')

diff --git a/2015/04/solve.c b/2015/04/solve.c
new file mode 100644
index 0000000..94246d4
--- /dev/null
+++ b/2015/04/solve.c
@@ -0,0 +1,118 @@
+#include <limits.h>
+#include <openssl/md5.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+
+#define FORLINE                                                                                    \
+	char *line = NULL;                                                                         \
+	size_t len = 0;                                                                            \
+	while (getline(&line, &len, fp) != EOF)
+#define FREELINE                                                                                   \
+	if (line)                                                                                  \
+	free(line)
+
+#define FORCH                                                                                      \
+	char ch = 0;                                                                               \
+	while ((ch = fgetc(fp)) != EOF)
+
+#define WHOLE                                                                                      \
+	fseek(fp, 0, SEEK_END);                                                                    \
+	long fsize = ftell(fp);                                                                    \
+	fseek(fp, 0, SEEK_SET);                                                                    \
+	char *data = malloc(fsize + 1);                                                            \
+	fread(data, 1, fsize, fp);                                                                 \
+	data[fsize] = 0;                                                                           \
+	data[fsize--] = 0
+
+#define FREEWHOLE free(data)
+
+static int part_one(FILE *fp)
+{
+	int res = 0;
+
+	WHOLE;
+
+	char *string = malloc(fsize + 64);
+	strcpy(string, data);
+
+	while (1) {
+		res++;
+
+		int cnt = sprintf(string + fsize, "%d", res);
+
+		char out[64] = { 0 };
+		unsigned char *hash =
+			MD5((unsigned char *)string, fsize + cnt, (unsigned char *)out);
+		/* for (int i = 0; i < 16; i++) */
+		/* 	printf("%02x", hash[i]); */
+		/* putchar('\n'); */
+
+		int sum = 0;
+		for (int i = 0; i < 2; i++)
+			sum += hash[i];
+		sum += hash[2] & 0xf0;
+		if (sum == 0)
+			break;
+	}
+
+	free(string);
+	FREEWHOLE;
+
+	return res;
+}
+
+static int part_two(FILE *fp)
+{
+	int res = 0;
+
+	WHOLE;
+
+	char *string = malloc(fsize + 64);
+	strcpy(string, data);
+
+	while (1) {
+		res++;
+
+		int cnt = sprintf(string + fsize, "%d", res);
+
+		char out[64] = { 0 };
+		unsigned char *hash =
+			MD5((unsigned char *)string, fsize + cnt, (unsigned char *)out);
+		/* for (int i = 0; i < 16; i++) */
+		/* 	printf("%02x", hash[i]); */
+		/* putchar('\n'); */
+
+		int sum = 0;
+		for (int i = 0; i < 3; i++)
+			sum += hash[i];
+		if (sum == 0)
+			break;
+	}
+
+	free(string);
+	FREEWHOLE;
+
+	return res;
+}
+
+int main(int argc, char *argv[])
+{
+	(void)argc;
+	(void)argv;
+
+	FILE *fp = fopen("input", "r");
+	if (!fp)
+		exit(EXIT_FAILURE);
+
+	clock_t tic = clock();
+	printf("%d\n", part_one(fp));
+	rewind(fp);
+	printf("%d\n", part_two(fp));
+	clock_t toc = clock();
+	printf("TIME: %f seconds\n", (double)(toc - tic) / CLOCKS_PER_SEC);
+
+	fclose(fp);
+	return 0;
+}
-- 
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