Lesson 6

06/Optional02.c

@@ -0,0 +1,21 @@
+#include <stdio.h>
+
+int factorials[10] = {0};
+
+int factorial(int n) {
+    if (factorials[n-1] == 0) {
+        factorials[n-1] = n * factorial(n-1);
+    }
+    return factorials[n-1];
+}
+
+int main() {
+    int k = 0, sum = 0, i;
+    scanf("%d", &k);
+    factorials[0] = 1;
+    for (i = 1;i <= k; i++) {
+        sum += factorial(i);
+    }
+    printf("%d", sum);
+    return 0;
+}