Add day 13 part 1

3 files changed, 52 insertions, 0 deletions

diff --git a/13/input b/13/input
new file mode 100644
index 0000000..f9503fe
--- /dev/null
+++ b/13/input
@@ -0,0 +1,2 @@
+1005526
+37,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,41,x,x,x,x,x,x,x,x,x,587,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,13,19,x,x,x,23,x,x,x,x,x,29,x,733,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,17
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]));
+}
diff --git a/13/testinput b/13/testinput
new file mode 100644
index 0000000..d76f619
--- /dev/null
+++ b/13/testinput
@@ -0,0 +1,2 @@
+939
+7,13,x,x,59,x,31,19