day 4

day2_plasl.c

@@ -0,0 +1,130 @@
+#include "lib.h"
+
+#define DBG 0
+
+static
+unsigned char input[] = {
+#embed "day2_input.txt"
+};
+
+static
+unsigned char test[] = {
+#embed "day2_test.txt"
+};
+
+uint64_t ipow(uint64_t a, uint64_t b) {
+    uint64_t m = a;
+    for (;b;b--) m += a;
+    return m;
+}
+
+static
+uint64_t range(uint64_t start, uint64_t end, uint64_t len) {
+#if DBG
+    print("==\n");
+    printd(start); print(" "); printd(end); print("\n");
+#endif
+
+    if ((len & 1) == 1) {
+        return 0;
+    }
+
+    uint64_t divisor = ipow(10, len / 2);
+
+    uint64_t first = (start + divisor - 1) / divisor;
+    uint64_t second = end / divisor;
+
+#if DBG
+    print("\n");
+    printd(divisor); print("\n");
+    printd(first); print(" "); printd(second); print("\n");
+#endif
+
+    uint64_t r = (((second + first) * (second + 1 - first)) / 2) * divisor;
+
+#if DBG
+    printd(r); print("\n");
+#endif
+
+    return r;
+}
+
+static
+uint64_t do_part1(size_t file_len, unsigned char file[file_len]) {
+    unsigned char buffer[65535];
+    memcpy(buffer, file, file_len);
+    size_t size = file_len;
+    buffer[file_len-1] = ',';
+
+    uint64_t out = 0;
+    uint64_t i = 0;
+
+    while (i < size) {
+#if DBG
+        print("--------------\n");
+#endif
+        uint64_t startlen = 0, endlen = 0;
+        uint64_t start = grabnum(buffer+i, NULL);
+
+        while (buffer[i] != '-') {
+            i++;
+            startlen++;
+        }
+        i++;
+
+        uint64_t end = grabnum(buffer+i, NULL);
+
+        while (buffer[i] != ',') {
+            i++;
+            endlen++;
+        }
+        i++;
+
+#if DBG
+        printd(startlen); print(" "); printd(start); print((char[]){ 10 });
+        printd(startlen); print(" "); printd(start); print((char[]){ 10 });
+#endif
+
+        if (endlen != startlen) {
+            out += range(start, ipow(10, startlen) - 1, startlen)
+                +  range(ipow(10, startlen), end, endlen);
+        } else {
+            out += range(start, end, startlen);
+        }
+
+#if DBG
+        print((char[]) { 10 });
+#endif
+    }
+
+    return out;
+}
+
+#define RUN_TEST1 1
+#define RUN_PART1 1
+
+#define TEST1_EXPECT 0x1227775554l
+
+void run() {
+    volatile uintptr_t s = (uintptr_t)&s;
+    printh(s);
+    print("\n");
+#if RUN_TEST1
+    print("PART 1 TEST: ");
+    if (uint64_t v = do_part1(countof(test), test); v != TEST1_EXPECT) {
+        print("FAILED (got ");
+        printd(v);
+        print(", expected " xstr(TEST1_EXPECT) ")\n");
+    } else {
+        print("PASSED\n");
+    }
+#endif
+
+#if RUN_PART1
+    print("PART 1 RESULT: ");
+    printd(do_part1(countof(input), input));
+    print("\n");
+#endif
+
+    exit_group(0);
+}