advent2023

commit 01e91e73f0dd2caaffbda55b347731505f566efb
parent 8d6c90c171aa8ab3713367cbe9c3b1436f590a70
Author: bsandro <email@bsandro.tech>
Date:   Wed, 17 Jan 2024 17:55:53 +0200

day 09 p2

Diffstat:
M
day09/puzzle.c
 | 
24
+++++++++++++++---------

1 file changed, 15 insertions(+), 9 deletions(-)
diff --git a/day09/puzzle.c b/day09/puzzle.c
@@ -44,13 +44,21 @@ int IntArray_Diff(IntArray *a) {
 	for (int i=1; i<a->len; ++i) {
 		IntArray_Add(&n, a->values[i] - a->values[i-1]);
 	}
-	//printf("diff array:\n");
-	//IntArray_Print(&n);
 	int diff = IntArray_Diff(&n);
-	//printf("d=%d\n", diff);
 	return a->values[a->len-1]+diff;
 }
 
+int IntArray_Rdiff(IntArray *a) {
+	if (IntArray_Same(a)) return a->values[0];
+	if (a->len==1) { printf("error: array of len 1\n"); exit(-1); }
+	IntArray n = {0};
+	for (int i=0; i<a->len-1; ++i) {
+		IntArray_Add(&n, a->values[i+1] - a->values[i]);
+	}
+	int diff = IntArray_Rdiff(&n);
+	return a->values[0]-diff;
+}
+
 void puzzle(const char *filename, long long *result1, long long *result2) {
 	FILE *infile = fopen(filename, "r");
 	if (infile == NULL) {
@@ -71,13 +79,11 @@ void puzzle(const char *filename, long long *result1, long long *result2) {
 		}
 		free(s);
 
-		/*printf("----- readings: -----\n");
-		IntArray_Print(&readings);
-		printf("---------------------\n");*/
+		int diff1 = IntArray_Diff(&readings);
+		*result1 += diff1;
 
-		int diff = IntArray_Diff(&readings);
-		//printf("diffs:%d\n", diff);
-		*result1 += diff;
+		int diff2 = IntArray_Rdiff(&readings);
+		*result2 += diff2;
 		//@todo list_free ?
 		++line_num;
 		bzero(buf, STR_LEN);