1 files changed, 39 insertions, 0 deletions
diff --git a/šola/p2/dn/DN04b_63230317.c b/šola/p2/dn/DN04b_63230317.c
new file mode 100644
index 0000000..105890a
--- /dev/null
+++ b/šola/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);
+}