From 2bb84babfcdb0f6d1267ed4fde89c0da6749a83f Mon Sep 17 00:00:00 2001
From: flavis <christian@flavigny.de>
Date: Sun, 24 Nov 2019 23:57:43 +0100
Subject: [PATCH] add uebung5 programs

---
 ws2019/ipi/uebungen/perfectShuffle.cpp  | 77 +++++++++++++++++++++++++
 ws2019/ipi/uebungen/readSortedArray.cpp | 59 +++++++++++++++++++
 2 files changed, 136 insertions(+)
 create mode 100644 ws2019/ipi/uebungen/perfectShuffle.cpp
 create mode 100644 ws2019/ipi/uebungen/readSortedArray.cpp

diff --git a/ws2019/ipi/uebungen/perfectShuffle.cpp b/ws2019/ipi/uebungen/perfectShuffle.cpp
new file mode 100644
index 0000000..a2f529b
--- /dev/null
+++ b/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];
+            }
+        }
+    }
+}
diff --git a/ws2019/ipi/uebungen/readSortedArray.cpp b/ws2019/ipi/uebungen/readSortedArray.cpp
new file mode 100644
index 0000000..38c154d
--- /dev/null
+++ b/ws2019/ipi/uebungen/readSortedArray.cpp
@@ -0,0 +1,59 @@
+#include "cpp_headers/fcpp.hh"
+
+int main() {
+    print("Please enter 10 natural numbers, enter 0 to show the sorted array, -1 to quit");
+    // initialize the array with 0s
+    int numbers[10] = {0,0,0,0,0,0,0,0,0,0};
+    // ask 11 times for input
+    for (int i = 0; i < 11; i++) {
+        int input = enter_int("> ");
+        // quit on -1
+        if (input == -1) {
+            break;
+        // print the array on 0
+        } else if (input == 0) {
+            printf("Array = [");
+            for (int n = 0; n < 10; n++) {
+                // last number is printed with trailing bracket and newline
+                if (n == 9) {
+                    printf("%d]\n", numbers[n]);
+                // print out a single number with trailing space
+                } else {
+                    printf("%d ", numbers[n]);
+                }
+            }
+            break;
+        // if already full, quit
+        } else if (i >= 10) {
+            print("array already full, terminating");    
+            break;
+        // quit on invalid input
+        } else if (input < -1) {
+            print("input not allowed, terminating");
+            break;
+        // otherwise insert new input
+        } else {
+            // set last number to new input
+            numbers[i] = input;
+            // sort numbers from 0 to i
+            for (int k = 0; k < i; k++) {
+                // whenever we see a wrong ordered number
+                if (numbers[k] > numbers[k+1]) {
+                    int smaller = numbers[k+1];
+                    int bigger = numbers[k];
+                    // flip the numbers
+                    numbers[k] = smaller;
+                    numbers[k+1] = bigger;
+                    // and step back to compare with previous numbers
+                    if (k <= 1) {
+                        // there is no number before the first one
+                        k = 0;
+                    } else {
+                        // step back 2, because we are adding 1 each time
+                        k = k-2;
+                    }
+                }
+            }
+        }
+    }
+}