Day 6 part 2 complete! Plus a little cleanup in part 1. :)

Makefile

@@ -31,7 +31,7 @@ day5: day5/p1.c day5/p2.c
 
 day6: day6/p1.c day6/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*

day6/p1.c

@@ -42,8 +42,7 @@ int main(int argc, char **argv) {
 
     for (ssize_t i = time_line_length-2, j = 0;;) {
         while (!ISDIGIT(time_line[i])) {
-            --i;
-            if (time_line[i] == ':')
+            if (time_line[--i] == ':')
                 goto tl_end;
         }
 
@@ -58,8 +57,7 @@ int main(int argc, char **argv) {
 
     for (ssize_t i = distance_line_length-2, j = 0;;) {
         while (!ISDIGIT(distance_line[i])) {
-            --i;
-            if (distance_line[i] == ':')
+            if (distance_line[--i] == ':')
                 goto dl_end;
         }
 
@@ -78,8 +76,6 @@ int main(int argc, char **argv) {
         uint64_t tmid = times[i] / 2;
         uint64_t ways = 0;
 
-        printf(":: %lu\n", times[i]);
-
         for (uint64_t ht = tmid; ht <= times[i]; ++ht) {
             if (ht * (times[i] - ht) > distances[i])
                 ++ways;
@@ -94,8 +90,6 @@ int main(int argc, char **argv) {
                 break;
         }
 
-        printf(":: %lu = %lu\n", times[i], ways);
-
         total_ways *= ways;
     }
 

day6/p2.c

@@ -0,0 +1,84 @@
+#define  _GNU_SOURCE
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdint.h>
+#include <stdbool.h>
+
+
+#define ISDIGIT(c) (c >= 0x30 && c <= 0x39)
+
+int main(int argc, char **argv) {
+    FILE *input;
+    size_t line_buf_length = 0;
+
+    if (argc == 1 || argv[1][0] == '-')
+		input = stdin;
+	else if ((input = fopen(argv[1], "r")) == NULL) {
+		fprintf(stderr, "Cannot open file %s\n", argv[1]);
+		return -1;
+	}
+
+    char *time_line = NULL, *distance_line = NULL;
+    ssize_t time_line_length = 0, distance_line_length = 0;
+
+    if ((time_line_length = getline(&time_line, &line_buf_length, input)) == -1) {
+        fprintf(stderr, "No time line in a file %s.", argv[1]);
+        return -1;
+    }
+
+    if ((distance_line_length = getline(&distance_line, &line_buf_length, input)) == -1) {
+        fprintf(stderr, "No distance line in a file %s.", argv[1]);
+        return -1;
+    }
+
+    uint64_t time = 0, distance = 0;
+
+    for (ssize_t i = time_line_length-2, m = 1;; --i) {
+        while (!ISDIGIT(time_line[i])) {
+            if (time_line[--i] == ':')
+                goto tl_end;
+        }
+
+        while (ISDIGIT(time_line[i])) {
+            time += (time_line[i--]&0xf) * m;
+            m *= 10;
+        }
+    }
+    tl_end:
+
+    for (ssize_t i = distance_line_length-2, m = 1;; --i) {
+        while (!ISDIGIT(distance_line[i])) {
+            if (distance_line[--i] == ':')
+                goto dl_end;
+        }
+
+        while (ISDIGIT(distance_line[i])) {
+            distance += (distance_line[i--]&0xf) * m;
+            m *= 10;
+        }
+    }
+    dl_end:
+
+    uint64_t total_ways = 0;
+
+    uint64_t tmid = time / 2;
+
+    for (uint64_t ht = tmid; ht <= time; ++ht) {
+        if (ht * (time - ht) > distance)
+            ++total_ways;
+        else
+            break;
+    }
+
+    for (uint64_t ht = tmid-1; ht != 0; --ht) {
+        if (ht * (time - ht) > distance)
+            ++total_ways;
+        else
+            break;
+    }
+
+    printf("%lu\n", total_ways);
+
+    return 0;
+}