1 files changed, 18 insertions, 0 deletions
diff --git a/2019/day04.c b/2019/day04.c
new file mode 100644
index 0000000..3c31931
--- /dev/null
+++ b/2019/day04.c
@@ -0,0 +1,18 @@
+#include <stdio.h>
+#include <stdlib.h>
+int main(void) {
+	int min, max;
+	scanf("%d-%d", &min, &max);
+	int count = 0;
+	for (int n = min; n <= max; ++n) {
+		char str[7];
+		snprintf(str, sizeof(str), "%d", n);
+		int adj = 0, dec = 0;
+		for (int i = 1; i < 6; ++i) {
+			if (str[i] == str[i - 1]) adj = 1;
+			if (str[i] < str[i - 1]) dec = 1;
+		}
+		if (adj && !dec) count++;
+	}
+	printf("%d\n", count);
+}