add basic math functions

src/input.c

@@ -36,7 +36,7 @@ char *get_input(const char *path) {
     return buf;
 }
 
-char **split(const char *s, size_t *lsz, const char *delim) {
+char **split(char *s, size_t *lsz, const char *delim) {
     char **lines = NULL;
     char *t = strtok(s, delim);
     size_t n = 0;

src/math.c

@@ -0,0 +1,28 @@
+#include <string.h>
+
+#include "math.h"
+
+int max_int(int a, int b) {
+    if (a > b) {
+        return a;
+    }
+    return b;
+}
+
+int min_int(int a, int b) {
+    if (a < b) {
+        return a;
+    }
+    return b;
+}
+
+int binstr_to_int(const char *s) {
+    int n = 0, m = 1;
+    for (size_t i = strlen(s) - 1; i >= 0; --i) {
+        if (s[i] == '1') {
+            n += m;
+        }
+        m *= 2;
+    }
+    return n;
+}