From c4fbb0ad7fe9e3f5035a7f431b6887427556690c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Anton=20Luka=20=C5=A0ijanec?= <anton@sijanec.eu>
Date: Sun, 24 Mar 2024 12:42:20 +0100
Subject: dn04a in dn04b failed attempt
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dn04b: ni vseeno, a se premaknemo levo ali desno, ko a+b ni enako k,
treba se je pomakniti v smer, kjer pomik najmanj spremeni vrednost a.

ampak obstaja boljši in lažji implementacijski način za dn04b
---
 "\305\241ola/p2/dn/DN04a_63230317.c" | 30 +++++++++++++++++++++++++++
 "\305\241ola/p2/dn/DN04b_63230317.c" | 39 ++++++++++++++++++++++++++++++++++++
 2 files changed, 69 insertions(+)
 create mode 100644 "\305\241ola/p2/dn/DN04a_63230317.c"
 create mode 100644 "\305\241ola/p2/dn/DN04b_63230317.c"

diff --git "a/\305\241ola/p2/dn/DN04a_63230317.c" "b/\305\241ola/p2/dn/DN04a_63230317.c"
new file mode 100644
index 0000000..9c1c1b1
--- /dev/null
+++ "b/\305\241ola/p2/dn/DN04a_63230317.c"
@@ -0,0 +1,30 @@
+#include <stdio.h>
+#include <stdbool.h>
+int main (void) {
+	int n;
+	scanf("%d", &n);
+	int a[2*n];
+	unsigned int lsum = 0;
+	unsigned int rsum = 0;
+	for (int i = 0; i < 2*n; i++)
+		scanf("%d", &a[i]);
+	for (int k = 0;; k++) {
+		if (lsum == rsum) {
+			bool pravilno = true;
+			for (int j = 0; j < n; j++) {
+				// fprintf(stderr, "%d\t%d\t%d\t%d\n", j, a[j], (n+(n-k+j) % n), a[(n+(n-k+j) % n)]);
+				if (a[j] == a[n+(n-k+j) % n])
+					continue;
+				pravilno = false;
+				break;
+			}
+			if (pravilno) {
+				printf("%d\n", k);
+				break;
+			}
+		}
+		lsum += a[k];
+		rsum += a[2*n-1-k];
+
+	}
+}
diff --git "a/\305\241ola/p2/dn/DN04b_63230317.c" "b/\305\241ola/p2/dn/DN04b_63230317.c"
new file mode 100644
index 0000000..105890a
--- /dev/null
+++ "b/\305\241ola/p2/dn/DN04b_63230317.c"
@@ -0,0 +1,39 @@
+#include <stdio.h>
+#include <stdbool.h>
+int main (void) {
+	int n, k, s = 0;
+	scanf("%d %d", &n, &k);
+	int a[n];
+	for (int i = 0; i < n; i++)
+		scanf("%d", &a[i]);
+	int d, l = n-1;
+	for (int i = 0; i < n-1; i++)
+		if (2*a[i] <= k && 2*a[i+1] > k)
+			l = i;
+	d = l;
+	fprintf(stderr, "l je %d, d je %d\n", l, d);
+	do {
+		if (a[l]+a[d] == k) {
+			int lc = l;
+			int dc = d;
+			int add = 0;
+			while (lc >= 0 && a[lc] == a[l])
+				lc--;
+			while (dc <= n-1 && a[dc] == a[d])
+				dc++;
+			if (a[l] == a[d]) // (dc-lc) choose 2
+				add = ((dc-lc-1)*n)/2;
+			else
+				add = (d-dc+1)*(lc-l+1);
+			fprintf(stderr, "l=%d, d=%d, a[l]=%d, a[d]=%d, lc=%d, dc=%d, add=%d\n", l, d, a[l], a[d], lc, dc, add);
+			l = lc;
+			d = dc;
+			s += add;
+		}
+		if (l-1 >= 0)
+			l--;
+		if (d+1 < n)
+			d++;
+	} while (d < n-1 || l > 0);
+	printf("%d\n", s);
+}
-- 
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