day 6

Makefile

@@ -14,13 +14,13 @@ LFLAGS = -Ttext=C475000 -static -nostdlib -no-pie
 
 all: $(BINS)
 
-%.elf: %.o start.o | %.c lib.h $(MUSLOBJS)
+%.elf: %.o start.o | %.c $(MUSLOBJS)
 	ld -o $@ $(LFLAGS) start.o $< $(MUSLOBJS)
 
 start.o: start.s
 	nasm -f elf64 -o $@ $<
 
-%.o: %.c
+%.o: %.c | lib.h
 	gcc-tree -o $@ $(CFLAGS) $<
 
 clean:

day0.h

@@ -3,20 +3,20 @@
 #define DBG 0
 
 static
-unsigned char input[] = {
+ch input[] = {
 #embed "day0_input.txt"
 };
 
 static
-unsigned char test[] = {
+ch test[] = {
 #embed "day0_test.txt"
 };
 
 
 static
-unsigned long do_part1(size_t file_len, unsigned char file[file_len]) {
+num do_part1(size_t file_len, ch file[file_len]) {
-    unsigned char *s = file;
+    ch *s = file;
-    unsigned long result = 0;
+    num result = 0;
 
 #if DBG
     print("\n");
@@ -30,18 +30,8 @@ do {
 }
 
 static
-unsigned long do_part2(size_t file_len, unsigned char file[file_len]) {
+num do_part2(size_t file_len, ch file[file_len]) {
-    unsigned char *s = file;
+    num result = 0;
-    unsigned long result = 0;
-
-#if DBG
-    print("\n");
-#endif
-
-do {
-    s++;
-} while (s != &file[file_len]);
-
     return result;
 }
 
@@ -56,7 +46,7 @@ do {
 void run() {
 #if RUN_TEST1
     print("PART 1 TEST: ");
-    if (unsigned long v = do_part1(countof(test), test); v != TEST1_EXPECT) {
+    if (num v = do_part1(countof(test), test); v != TEST1_EXPECT) {
         print("FAILED (got ");
         printd(v);
         print(", expected " xstr(TEST1_EXPECT) ")\n");
@@ -73,7 +63,7 @@ void run() {
 
 #if RUN_TEST2
     print("PART 2 TEST: ");
-    if (unsigned long v = do_part2(countof(test), test); v != TEST2_EXPECT) {
+    if (num v = do_part2(countof(test), test); v != TEST2_EXPECT) {
         print("FAILED (got ");
         printd(v);
         print(", expected " xstr(TEST2_EXPECT) ")\n");

day6.c

@@ -0,0 +1,245 @@
+#include "lib.h"
+
+#define DBG 1
+
+static
+ch input[] = {
+#embed "day6_input.txt"
+};
+
+static
+ch test[] = {
+#embed "day6_test.txt"
+};
+
+
+static
+num do_part1(size_t file_len, ch file[file_len]) {
+    ch *s = file;
+    num result = 0;
+
+#if DBG
+    print("\n");
+#endif
+
+    while (*s != 10) s++;
+    num stride = s - file + 1;
+
+    s = file;
+    while (*s != '+' && *s != '*') s += stride;
+    num heightb = (s - file);
+    num height  = (s - file) / stride;
+    ch *op = s;
+
+#if DBG
+    print("STRIDE\t"); printd(stride); print("\n");
+    print("HEIGHT\t"); printd(height); print("\n");
+#endif
+
+    // constructing a pointer more than 1 past the end of an array
+    // is UB, sadly, so we'll use offsets
+    num op_off = op - file;
+    s = file;
+    do {
+        num ledge_off = op_off - heightb;
+        if (s[op_off] == '+') {
+            num a = 0;
+            num rem = height;
+            do {
+                ch *t = s + ledge_off;
+                while (*t < '0') t++;
+                num b = grabnum(t, NULL);
+#if DBG
+                if (rem < height) { print("\t+\t"); }
+                printd(b);
+#endif
+                a += b;
+                ledge_off += stride;
+                rem--;
+            } while (rem);
+            result += a;
+#if DBG
+            print("\t= "); printd(a); print("\n");
+#endif
+        } else if (s[op_off] == '*') {
+            num a = 1;
+            num rem = height;
+            do {
+                ch *t = s + ledge_off;
+                while (*t < '0') t++;
+                num b = grabnum(t, NULL);
+#if DBG
+                if (rem < height) { print("\t*\t"); }
+                printd(b);
+#endif
+                a *= b;
+                ledge_off += stride;
+                rem--;
+            } while (rem);
+            result += a;
+#if DBG
+            print("\t= "); printd(a); print("\n");
+#endif
+        }
+#if DBG
+        else {
+            print("INVALID OP\n");
+            exit_group(-1);
+        }
+#endif
+        op_off++;
+        while (op_off < file_len) {
+            if (s[op_off] == '+' || s[op_off] == '*')
+                break;
+            op_off++;
+        }
+    } while (op_off < file_len);
+
+    return result;
+}
+
+static
+num do_part2(size_t file_len, unsigned char file[file_len]) {
+    ch *s = file;
+    num result = 0;
+
+#if DBG
+    print("\n");
+#endif
+
+    while (*s != 10) s++;
+    num stride = s - file + 1;
+
+    s = file;
+    while (*s != '+' && *s != '*') s += stride;
+    num heightb = (s - file);
+    num height  = (s - file) / stride;
+    ch *op = s;
+
+#if DBG
+    print("STRIDE\t"); printd(stride); print("\n");
+    print("HEIGHT\t"); printd(height); print("\n");
+#endif
+
+    // constructing a pointer more than 1 past the end of an array
+    // is UB, sadly, so we'll use offsets
+    num fop_off = op - file;
+    num prev_op_off = fop_off + stride - 1;
+    s = file;
+    do {
+        // we don't need to do these in the same order as the example
+        // because both these operations are commutative.
+        // but you know what? we can anyway. for fun. and pretty output
+        num op_off = prev_op_off - 1;
+        while (s[op_off] != '+' && s[op_off] != '*' && s[op_off] != '\n')
+            op_off--;
+        num ledge_off = op_off - heightb;
+        num redge_off = (s[prev_op_off] == '\n' ? -1 : -2) + prev_op_off - heightb;
+        if (s[op_off] == '+') {
+            num a = 0;
+            num rem = redge_off - ledge_off + 1;
+            num frem = rem;
+            do {
+                num b = 0;
+                ch *t = s + redge_off;
+                for (num i = height; i; i--,t+=stride) {
+                    if (*t >= '0') {
+                        b *= 10;
+                        b += *t - '0';
+                    }
+                }
+#if DBG
+                if (rem < frem) { print("\t+\t"); }
+                printd(b);
+#endif
+                a += b;
+                redge_off--;
+                rem--;
+            } while (rem);
+            result += a;
+#if DBG
+            print("\t=\t"); printd(a); print("\n");
+#endif
+        } else if (s[op_off] == '*') {
+            num a = 1;
+            num rem = redge_off - ledge_off + 1;
+            num frem = rem;
+            do {
+                num b = 0;
+                ch *t = s + redge_off;
+                for (num i = height; i; i--,t+=stride) {
+                    if (*t >= '0') {
+                        b *= 10;
+                        b += *t - '0';
+                    }
+                }
+#if DBG
+                if (rem < frem) { print("\t*\t"); }
+                printd(b);
+#endif
+                a *= b;
+                redge_off--;
+                rem--;
+            } while (rem);
+            result += a;
+#if DBG
+            print("\t=\t"); printd(a); print("\n");
+#endif
+        }
+#if DBG
+        else {
+            print("INVALID OP\n");
+            exit_group(-1);
+        }
+#endif
+        prev_op_off = op_off;
+    } while (prev_op_off != fop_off);
+
+    return result;
+}
+
+#define RUN_TEST1 1
+#define RUN_PART1 1
+#define RUN_TEST2 1
+#define RUN_PART2 1
+
+#define TEST1_EXPECT 4277556
+#define TEST2_EXPECT 3263827
+
+void run() {
+#if RUN_TEST1
+    print("PART 1 TEST: ");
+    if (num 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 (num 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);
+}

lib.h

@@ -35,6 +35,7 @@ void exit_group(uint64_t code) {
 
 typedef uint64_t bcdint;
 typedef uint64_t num;
+typedef unsigned char ch;
 
 static
 void printns(size_t len, unsigned char chars[len]) {