day 4

day4.c

@@ -0,0 +1,207 @@
+#include "lib.h"
+
+#define DBG 0
+
+static
+unsigned char input[] = {
+#embed "day4_input.txt"
+};
+
+static
+unsigned char test[] = {
+#embed "day4_test.txt"
+};
+
+static
+unsigned char buf[UINT16_MAX];
+
+static
+unsigned long do_part1(size_t file_len, unsigned char file[file_len]) {
+    unsigned char *s = file, *d = buf;
+    unsigned long result = 0;
+
+#if DBG
+    print("\n");
+#endif
+
+    unsigned file_stride;
+    while (*s != '\n') s++;
+    file_stride = s - file + 1;
+    s = file;
+
+    unsigned line_count = file_len / file_stride;
+
+    unsigned line_stride = file_stride + 1;
+
+    memset(d, '0', sizeof(buf));
+
+#if DBG
+    printh(file_stride); print("\n");
+    printh(line_stride * (line_count + 2)); print("\n");
+#endif
+
+#if DBG
+    printns(line_stride, d); print("\n");
+#endif
+    d += line_stride;
+    do {
+        memcpy(d + 1, s, file_stride - 1);
+#if DBG
+        printns(line_stride, d); print("\n");
+#endif
+        d += line_stride;
+        s += file_stride;
+    } while (s != &file[file_len]);
+#if DBG
+    printns(line_stride, d); print("\n");
+#endif
+
+    unsigned char *l = buf + line_stride + 1;
+    for (unsigned i = line_count; i; i--) {
+        d = l;
+        for (unsigned j = line_stride - 2; j; j--) {
+            if (*d == '@') {
+                unsigned neighbors = 0
+                    + (*(d - 1 - line_stride) == '@')
+                    + (*(d - 0 - line_stride) == '@')
+                    + (*(d + 1 - line_stride) == '@')
+                    + (*(d - 1 - 0) == '@')
+                    + (*(d + 1 - 0) == '@')
+                    + (*(d - 1 + line_stride) == '@')
+                    + (*(d - 0 + line_stride) == '@')
+                    + (*(d + 1 + line_stride) == '@');
+                if (neighbors < 4) {
+                    result++;
+                }
+            }
+            d++;
+        }
+        l += line_stride;
+    }
+
+    return result;
+}
+
+static
+unsigned long do_part2(size_t file_len, unsigned char file[file_len]) {
+    unsigned char *s = file, *d = buf;
+    unsigned long result = 0;
+
+#if DBG
+    print("\n");
+#endif
+
+    unsigned file_stride;
+    while (*s != '\n') s++;
+    file_stride = s - file + 1;
+    s = file;
+
+    unsigned line_count = file_len / file_stride;
+
+    unsigned line_stride = file_stride + 1;
+
+    memset(d, '0', sizeof(buf));
+
+#if DBG
+    printh(file_stride); print("\n");
+    printh(line_stride * (line_count + 2)); print("\n");
+#endif
+
+#if DBG
+    printns(line_stride, d); print("\n");
+#endif
+    d += line_stride;
+    do {
+        memcpy(d + 1, s, file_stride - 1);
+#if DBG
+        printns(line_stride, d); print("\n");
+#endif
+        d += line_stride;
+        s += file_stride;
+    } while (s != &file[file_len]);
+#if DBG
+    printns(line_stride, d); print("\n");
+#endif
+
+    unsigned char *l = buf + line_stride + 1;
+    for (unsigned i = line_count; i; i--) {
+line_start:
+        d = l;
+        for (unsigned j = line_stride - 2; j; j--) {
+            if (*d == '@') {
+                unsigned neighbors = 0
+                    + (*(d - 1 - line_stride) == '@')
+                    + (*(d - 0 - line_stride) == '@')
+                    + (*(d + 1 - line_stride) == '@')
+                    + (*(d - 1 - 0) == '@')
+                    + (*(d + 1 - 0) == '@')
+                    + (*(d - 1 + line_stride) == '@')
+                    + (*(d - 0 + line_stride) == '@')
+                    + (*(d + 1 + line_stride) == '@');
+                if (neighbors < 4) {
+                    *d = '.';
+                    result++;
+                    if (i > line_count-1) {
+                        i = line_count;
+                        l = buf + line_stride + 1;
+                        goto line_start;
+                    } else {
+                        i += 1;
+                        l -= line_stride * 1;
+                        goto line_start;
+                    }
+                }
+            }
+            d++;
+        }
+        l += line_stride;
+    }
+
+    return result;
+}
+
+#define RUN_TEST1 1
+#define RUN_PART1 1
+#define RUN_TEST2 1
+#define RUN_PART2 1
+
+#define TEST1_EXPECT 13
+#define TEST2_EXPECT 43
+
+void run() {
+#if RUN_TEST1
+    print("PART 1 TEST: ");
+    if (unsigned long 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
+
+#if RUN_TEST2
+    print("PART 2 TEST: ");
+    if (unsigned long v = do_part2(countof(test), test); v != TEST2_EXPECT) {
+        print("FAILED (got ");
+        printd(v);
+        print(", expected " xstr(TEST2_EXPECT) ")\n");
+    } else {
+        print("PASSED\n");
+    }
+#endif
+
+#if RUN_PART2
+    print("PART 2 RESULT: ");
+    printd(do_part2(countof(input), input));
+    print("\n");
+#endif
+
+    exit_group(0);
+}