Feature: Added a possible Solution

Refactored the Method fl to show
what is actually going on.

fl.cpp

-//
-// Created by Kai Renz on 02.11.23.
-//
-
-int fl(int* i,int l) {
-    for (int k=0;k<l;k++) {
-        if (i[k]<0||i[k]>=l) {
-            i[k]=-1;
-        } else {
-            if (i[k]!=k) {
-                int v=i[k];
-                if (i[k]!=k) {
-                    i[k]=-1;
-                }
-                while (v>=0&&v<l&&i[v]!=v) {
-                    int t=i[v];
-                    i[v]=v;
-                    v=t;
-                }
-            }
-        }
+
+static const int UNUSED = -1;
+
+bool canSwap(const int *array, int length, int valueAtPosition);
+int doSwap(int *array, int valueAtPosition);
+
+void doStuffAtPosition(int *array, int length, int position);
+
+void handleValidValueAtPosition(int *array, int length, int position);
+
+bool hasUnallowedValueAtPosition(const int *array, int length, int position);
+
+int findeLueckeInArray(int* array, int length) {
+    for (int position=0; position < length; position++) {
+        doStuffAtPosition(array, length, position);
+    }
+    int positionLuecke=0;
+    for (; positionLuecke < length && array[positionLuecke] != UNUSED; positionLuecke++) {}
+    return positionLuecke;
+}
+
+void doStuffAtPosition(int *array, int length, int position) {
+    if (hasUnallowedValueAtPosition(array, length, position)) {
+        array[position]= UNUSED;
+        return;
     }
-    int m=0;
-    for (;m<l&&i[m]!=-1;m++) {}
-    return m;
-}
+
+    if (array[position] == position) {
+        return;
+    }
\ No newline at end of file
+
+    handleValidValueAtPosition(array, length, position);
+}
+
+bool hasUnallowedValueAtPosition(const int *array, int length, int position) {
+    return array[position] < 0 || array[position] >= length; }
+
+void handleValidValueAtPosition(int *array, int length, int position) {
+    int valueAtPosition=array[position];
+    array[position]= UNUSED;
+    while (canSwap(array, length, valueAtPosition)) {
+        valueAtPosition = doSwap(array, valueAtPosition);
+    }
+}
+
+
+int doSwap(int *array, int valueAtPosition) {
+    int valueAtFuturePosition=array[valueAtPosition];
+    array[valueAtPosition]=valueAtPosition;
+    return valueAtFuturePosition;
+}
+
+bool canSwap(const int *array, int length, int valueAtPosition) {
+    return valueAtPosition >= 0 && valueAtPosition < length
+               && array[valueAtPosition] != valueAtPosition;
+}

main.cpp

 #include <iostream>
 
-int fl(int *i,int l);
+int findeLueckeInArray(int *array, int length);
 
 void expect(bool b, std::string text) {
     if (!b) {
@@ -23,15 +23,15 @@ int main() {
             (int[]) {4, -1,1,2,3}
     };
 
-    expect(fl( v[0],3) == 3,"Expected to be 3");
-    expect(fl( v[1],2) == 0,"Expected to be 0");
-    expect(fl( v[2],3) == 1,"Expected to be 1");
-    expect(fl( v[3],5) == 4,"Expected to be 4");
-    expect(fl( v[4],5) == 4,"Expected to be 4");
-    expect(fl( v[5],5) == 0,"Expected to be 0");
-    expect(fl( v[6],5) == 4,"Expected to be 4");
-    expect(fl( v[7],5) == 5,"Expected to be 5");
-    expect(fl( v[8],5) == 0,"Expected to be 0");
+    expect(findeLueckeInArray(v[0], 3) == 3, "Expected to be 3");
+    expect(findeLueckeInArray(v[1], 2) == 0, "Expected to be 0");
+    expect(findeLueckeInArray(v[2], 3) == 1, "Expected to be 1");
+    expect(findeLueckeInArray(v[3], 5) == 4, "Expected to be 4");
+    expect(findeLueckeInArray(v[4], 5) == 4, "Expected to be 4");
+    expect(findeLueckeInArray(v[5], 5) == 0, "Expected to be 0");
+    expect(findeLueckeInArray(v[6], 5) == 4, "Expected to be 4");
+    expect(findeLueckeInArray(v[7], 5) == 5, "Expected to be 5");
+    expect(findeLueckeInArray(v[8], 5) == 0, "Expected to be 0");
 
     std::cout << "Success!";