Exercise 7

Added Exercise 7 to the repository

Informatik_I/Exercise_7/Task_2/README.org

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+#+title: Task 2: Bitstrings up to n
+
+#+author: JirR02
+* Task
+:PROPERTIES:
+:CUSTOM_ID: task
+:END:
+Your task is implementing the function =all_bitstrings_up_to_n= in
+=solution.cpp= which generates all bitstrings up to length \(n\) in
+ascending order. The generated bitstrings are returned in a
+=std::vector<std::string>=.
+
+*Note*: It is *mandatory* to use *recursive implementation* for this
+task.
+
+* Input & Output
+:PROPERTIES:
+:CUSTOM_ID: input-output
+:END:
+The program first prompts you to enter the bitstring length \(n\). It
+then calls the function =all_bitstrings_up_to_n= and prints the returned
+bitstrings to the console.
+
+** Example
+:PROPERTIES:
+:CUSTOM_ID: example
+:END:
+#+begin_src sh
+Bitstring length: 2
+Bitstrings up to length 2
+
+0
+1
+00
+01
+10
+11
+#+end_src
+
+*Note*: The empty line after Bitstrings up to length 2 is actually the
+bitstring of length \(0\).
+
+*Note*: The autograder will only accept output that exactly matches the
+expected result. Therefore, do not output anything with =std::cout= in
+the =all_bitstrings_up_to_n= function. For debugging messages, use
+=std::cerr= as in:
+
+#+begin_src cpp
+std::cerr << "This is a test message." << std::endl;
+#+end_src
+
+Those will be ignored by the autograder.
+
+* Solution
+:PROPERTIES:
+:CUSTOM_ID: solution
+:END:
+#+begin_src cpp
+#include "solution.h"
+using vec = std::vector<std::string>;
+using str = std::string;
+
+void bitstring(vec &res, str ram, int l) {
+  if (l == 0) {
+    res.push_back(ram);
+    return;
+  }
+
+  bitstring(res, ram + "0", l - 1);
+  bitstring(res, ram + "1", l - 1);
+}
+
+void recursion(int count, int n, vec &res) {
+  if (count > n)
+  return;
+
+  bitstring(res, "", count);
+  recursion(count + 1, n, res);
+}
+
+vec all_bitstrings_up_to_n(int n) {
+  vec res;
+
+  recursion(0, n, res);
+
+  return res;
+}
+#+end_src