From fabaaffe11c43d052f52add7ea0ed75e18ce533e Mon Sep 17 00:00:00 2001
From: "Alexander \"Arav\" Andreev" <me@arav.su>
Date: Sun, 3 Dec 2023 18:27:32 +0400
Subject: [PATCH] Day 3 part 2 complete!

---
 Makefile  |   2 +-
 day3/p2.c | 115 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 test      |   5 ++-
 3 files changed, 120 insertions(+), 2 deletions(-)
 create mode 100644 day3/p2.c

diff --git a/Makefile b/Makefile
index f30a7f9..b16408e 100644
--- a/Makefile
+++ b/Makefile
@@ -19,7 +19,7 @@ day2: day2/p1.c day2/p2.c
 
 day3: day3/p1.c day3/p2.c
 	${CC} ${CFLAGS} $@/p1.c -o bin/$@p1
-# ${CC} ${CFLAGS} $@/p2.c -o bin/$@p2
+	${CC} ${CFLAGS} $@/p2.c -o bin/$@p2
 
 clean:
 	rm -f bin/day*p*
\ No newline at end of file
diff --git a/day3/p2.c b/day3/p2.c
new file mode 100644
index 0000000..1795cd1
--- /dev/null
+++ b/day3/p2.c
@@ -0,0 +1,115 @@
+#define  _GNU_SOURCE
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include <ctype.h>
+
+int32_t parse_number(char **engine, ssize_t i, ssize_t j);
+
+int main(int argc, char **argv) {
+    FILE *input;
+    char *line = NULL;
+    size_t line_length = 0;
+
+    if (argc == 1 || argv[1][0] == '-')
+		input = stdin;
+	else if ((input = fopen(argv[1], "r")) == NULL) {
+		printf("Cannot open file %s\n", argv[1]);
+		return -1;
+	}
+
+    char **engine = NULL;
+    ssize_t engine_line_size = 0;
+    ssize_t engine_lines = 0;
+
+    while (getline(&line, &line_length, input) != -1) {
+        ssize_t len = strlen(line)-1;
+        if (engine == NULL) {
+            engine = (char **) calloc(len, sizeof(char*));
+            engine_line_size = len;
+        }
+
+        engine[engine_lines] = (char*) calloc(len, sizeof(char));
+        memcpy(engine[engine_lines], line, len);
+        ++engine_lines;
+
+        memset(line, 0, line_length);
+    }
+
+    int32_t part_number = 0;
+
+    for (ssize_t i = engine_lines-1; i >= 0; --i) {
+        for (ssize_t j = engine_line_size-1; j >= 0; --j) {
+            if (engine[i][j] != '*')
+                continue;
+
+            int32_t n = 1;
+            int8_t p = 0;
+
+            if (isdigit(engine[i][j+1])) {
+                n *= parse_number(engine, i, j+1);
+                p++;
+            }
+            if (isdigit(engine[i][j-1])) {
+                n *= parse_number(engine, i, j-1);
+                p++;
+            }
+
+            if (isdigit(engine[i+1][j])) {
+                n *= parse_number(engine, i+1, j);
+                p++;
+            } else {
+                if (isdigit(engine[i+1][j+1])) {
+                    n *= parse_number(engine, i+1, j+1);
+                    p++;
+                }
+                if (isdigit(engine[i+1][j-1])) {
+                    n *= parse_number(engine, i+1, j-1);
+                    p++;
+                }
+            }
+
+            if (isdigit(engine[i-1][j])) {
+                n *= parse_number(engine, i-1, j);
+                p++;
+            } else {
+                if (isdigit(engine[i-1][j+1])) {
+                    n *= parse_number(engine, i-1, j+1);
+                    p++;
+                }
+                if (isdigit(engine[i-1][j-1])) {
+                    n *= parse_number(engine, i-1, j-1);
+                    p++;
+                }
+            }
+
+            if (p >= 2)
+                part_number += n;
+        }
+    }
+
+    for (ssize_t i = 0; i < engine_lines; ++i)
+        free(engine[i]);
+    free(engine);
+
+    printf("%d\n", part_number);
+
+    return 0;
+}
+
+int32_t parse_number(char **engine, ssize_t i, ssize_t j) {
+    int32_t n = 0;
+    int32_t multiplier = 1;
+
+    while (isdigit(engine[i][j+1])) j++;
+
+    while (isdigit(engine[i][j])) {
+        n += (engine[i][j]&0xf) * multiplier;
+        multiplier *= 10;
+        j--;
+    }
+
+    return n;
+}
\ No newline at end of file
diff --git a/test b/test
index 8b5eec8..0f46b94 100755
--- a/test
+++ b/test
@@ -10,4 +10,7 @@ echo "Day 1 with test data part 1 $(test_case 1 1 "test" "142"), and part 2 $(te
 echo "Day 1 with my data part 1 $(test_case 1 1 "my" "55621"), and part 2 $(test_case 1 2 "my" "53592").";
 
 echo "Day 2 with test data part 1 $(test_case 2 1 "test" "8"), and part 2 $(test_case 2 2 "test" "2286").";
-echo "Day 2 with my data part 1 $(test_case 2 1 "my" "2727"), and part 2 $(test_case 2 2 "my" "56580").";
\ No newline at end of file
+echo "Day 2 with my data part 1 $(test_case 2 1 "my" "2727"), and part 2 $(test_case 2 2 "my" "56580").";
+
+echo "Day 3 with test data part 1 $(test_case 3 1 "test" "4361"), and part 2 $(test_case 3 2 "test" "467835").";
+echo "Day 3 with my data part 1 $(test_case 3 1 "my" "550934"), and part 2 $(test_case 3 2 "my" "81997870").";
\ No newline at end of file