add uebung5 programs

ws2019/ipi/uebungen/perfectShuffle.cpp

@@ -0,0 +1,77 @@
+#include "cpp_headers/fcpp.hh"
+
+bool deck_check(int deck[], int n) {
+    for (int i = 0; i < n; i++) {
+        // compare deck with number at this position
+        // because initial deck is [0,1,2,3,..., n-1]
+        if (deck[i] != i) {
+            // if a difference is found, return false
+            return false;
+        }
+    }
+    // if no problem was found, deck is the original deck
+    return true;
+}
+
+int main() {
+    // query the amount of cards that should be shuffled
+    int size = enter_int("How many cards do you want to be shuffled? ");
+    // only shuffle even number of cards
+    if (size <= 0, size % 2 != 0) {
+        print("Invalid input, please enter an even number >= 2");
+        return 0;
+    }
+    // initialize the deck of cards
+    int deck[size];
+    for (int i = 0; i<size; i++) {
+        deck[i] = i;
+    }
+
+    // initialize a working array
+    int newdeck[size];
+
+    // perfect out shuffle
+    for (int times = 1; ;times++) {
+        // shuffle with perfect out
+        for (int i = 0; i<size/2; i++) {
+            newdeck[i*2] = deck[i];
+            newdeck[i*2+1] = deck[i+size/2];
+        }
+        // check if newdeck is the original deck
+        if (deck_check(newdeck, size)) {
+            // print out the amount of iterations needed
+            printf("We needed %d perfect out shuffle iterations to get back to the original deck\n", times);
+            break;
+        } else {
+            // otherwise set deck to newdeck
+            for (int i = 0; i <size; i++) {
+                deck[i] = newdeck[i];
+            }
+        }
+    }
+
+    // reset the deck
+    for (int i = 0; i<size; i++) {
+        deck[i] = i;
+    }
+    
+    // perfect in shuffle
+    for (int times = 1; ;times++) {
+        // shuffle with perfect in
+        for (int i = 0; i<size/2; i++) {
+            newdeck[i*2] = deck[i+size/2];
+            newdeck[i*2+1] = deck[i];
+        }
+        // check if newdeck is the original deck
+        if (deck_check(newdeck, size)) {
+            // print out the amount of iterations needed
+            printf("We needed %d perfect in shuffle iterations to get back to the original deck\n", times);
+            break;
+        } else {
+            // otherwise set deck to newdeck
+            for (int i = 0; i <size; i++) {
+                deck[i] = newdeck[i];
+            }
+        }
+    }
+}