From 49d0c908f24b2c193c9deed1716fe36061ba26a1 Mon Sep 17 00:00:00 2001
From: Bond_009 <bond.009@outlook.com>
Date: Sun, 28 Nov 2021 17:58:30 +0100
Subject: Add day 13 part 1

---
 13/part1.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)
 create mode 100644 13/part1.c

(limited to '13/part1.c')

diff --git a/13/part1.c b/13/part1.c
new file mode 100644
index 0000000..b62d007
--- /dev/null
+++ b/13/part1.c
@@ -0,0 +1,48 @@
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define BUFFER_SIZE 256
+#define MAX_INPUT_LEN 128
+
+int solve(const char *filename)
+{
+    FILE *file = fopen(filename, "r");
+
+    char buffer[BUFFER_SIZE] = { 0 };
+    fgets(buffer, BUFFER_SIZE, file);
+    int depart = atoi(buffer);
+    fgets(buffer, BUFFER_SIZE, file);
+    int bus_ids[MAX_INPUT_LEN] = { 0 };
+    bus_ids[0] = atoi(buffer);
+    int i = 1;
+    char *p = buffer;
+    while ((p = strchr(p, ','))) {
+        // x is never the last value, just keep looping we find a valid input
+        while (*++p == 'x') {
+            p += 1;
+        }
+
+        bus_ids[i++] = atoi(p);
+    }
+
+    int bus_id = 0;
+    int wait = INT32_MAX;
+    for (int j = 0; j < i; j++) {
+        int id = bus_ids[j];
+        int tmprem = id - (depart % id);
+        if (tmprem < wait) {
+            bus_id = id;
+            wait = tmprem;
+        }
+    }
+
+    fclose(file);
+    return bus_id * wait;
+}
+
+int main(int argc, char *argv[])
+{
+    printf("%i\n", solve(argv[argc - 1]));
+}
-- 
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