1 files changed, 56 insertions, 0 deletions
diff --git a/euler112.c b/euler112.c
new file mode 100644
index 0000000..e2414bd
--- /dev/null
+++ b/euler112.c
@@ -0,0 +1,56 @@
+#include <stdio.h>
+#include <assert.h>
+
+int isbouncy(int a)
+{
+	int d[2];
+	int incr;
+	if (a < 100)
+		return 0;
+
+	d[0] = a % 10;
+	d[1] = (a / 10) % 10;
+	a /= 100;
+	if (d[1] > d[0])
+		incr = 1;
+	else if (d[1] < d[0])
+		incr = -1;
+	else
+		incr = 0;
+
+	while (a > 0) {
+		d[0] = d[1];
+		d[1] = a % 10;
+		if (incr == 1 && d[1] < d[0])
+			return 1;
+		if (incr == -1 && d[1] > d[0])
+			return 1;
+		if (incr == 0) {
+			if (d[1] > d[0])
+				incr = 1;
+			else if (d[1] < d[0])
+				incr = -1;
+		}
+		a /= 10;
+	}
+	return 0;
+}
+
+int main()
+{
+	assert(isbouncy(66420) == 0);
+	assert(isbouncy(134468) == 0);
+	assert(isbouncy(155349) == 1);
+
+	int nbouncy = 0;
+	for (int i = 100; i <= 0x7fffffff; i++) {
+		if (isbouncy(i))
+			nbouncy++;
+
+		if (nbouncy * 100 / 99 == i) {
+			printf("%d\n", i);
+			break;
+		}
+	}
+}
+