cpp/recursion/kettles Source

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Description
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shown to student

Write a program <code>Kettles</code> with a recursive static method
<code>sing(n)</code> which prints the famous "kettles of tea" song.
For example, when <code>n</code> is 3, calling <code>sing(3)</code>
should print out
<pre>
3 kettles of tea on the wall
3 kettles of tea
take one down, pass it around
2 kettles of tea on the wall!
2 kettles of tea on the wall
2 kettles of tea
take one down, pass it around
1 kettles of tea on the wall!
1 kettles of tea on the wall
1 kettles of tea
take one down, pass it around
no more kettles of tea on the wall!
</pre>
<div>
<i>To sing this song, first sing the first four lines, and then sing
the song for a smaller value of n (unless you are done).</i>
This is the strategy that you can turn into
a recursive method.
</div>
Note that we require your song to say <code>1 kettles</code>
instead of the grammatically correct <code>1 kettle</code>. Fixing this
is left as a challenge for the thirsty.

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Engine
Choices
json list of string, bool pairs
e.g. [["good", true], ["bad", false]]

Correct answer
Template / Reference solution

Template / Reference solution

#include <iostream>
using namespace std;

// sings a well-known song about n kettles
void sing(int n) {
// print three lines
\[
cout << n << " kettles of tea on the wall" << endl;
cout << n << " kettles of tea" << endl;
cout << "take one down, pass it around" << endl;
]\
if (n > 1) {
// sing fourth line, with exclamation point!
\[
cout << n-1 << " kettles of tea on the wall!" << endl;
]\
// call sing recursively on remaining kettles
sing(\[n-1]\);
}
else {
// sing the final line, with exclamation point!
\[
cout << "no more kettles of tea on the wall!" << endl;
]\
}
}

int main() {
int n;
cin >> n;
sing(n);
}

Java test suite
See manual

C++ test suite
json list of stdin/args tests
e.g. [{"stdin":"hi", "args":["4", "5"]}, {"stdin":"noargs"}]
to just run once with no input use [{}]

[
{"stdin": "3"},
{"stdin": "1"},
{"stdin": "9"}
]

C++ test suite
See manual

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Property	Value
Description html markup shown to student	Write a program <code>Kettles</code> with a recursive static method <code>sing(n)</code> which prints the famous "kettles of tea" song. For example, when <code>n</code> is 3, calling <code>sing(3)</code> should print out <pre> 3 kettles of tea on the wall 3 kettles of tea take one down, pass it around 2 kettles of tea on the wall! 2 kettles of tea on the wall 2 kettles of tea take one down, pass it around 1 kettles of tea on the wall! 1 kettles of tea on the wall 1 kettles of tea take one down, pass it around no more kettles of tea on the wall! </pre> <div> <i>To sing this song, first sing the first four lines, and then sing the song for a smaller value of n (unless you are done).</i> This is the strategy that you can turn into a recursive method. </div> Note that we require your song to say <code>1 kettles</code> instead of the grammatically correct <code>1 kettle</code>. Fixing this is left as a challenge for the thirsty.
Epilogue html markup shown when solved	remove
Public permissions	remove
Remarks Comments, history, license, etc.	remove
Engine
Choices json list of string, bool pairs e.g. `[["good", true], ["bad", false]]`
Correct answer
Template / Reference solution
Template / Reference solution	#include <iostream> using namespace std; // sings a well-known song about n kettles void sing(int n) { // print three lines \[ cout << n << " kettles of tea on the wall" << endl; cout << n << " kettles of tea" << endl; cout << "take one down, pass it around" << endl; ]\ if (n > 1) { // sing fourth line, with exclamation point! \[ cout << n-1 << " kettles of tea on the wall!" << endl; ]\ // call sing recursively on remaining kettles sing(\[n-1]\); } else { // sing the final line, with exclamation point! \[ cout << "no more kettles of tea on the wall!" << endl; ]\ } } int main() { int n; cin >> n; sing(n); }
Java test suite See manual
C++ test suite json list of stdin/args tests e.g. `[{"stdin":"hi", "args":["4", "5"]}, {"stdin":"noargs"}]` to just run once with no input use `[{}]`	[ {"stdin": "3"}, {"stdin": "1"}, {"stdin": "9"} ]
C++ test suite See manual
Forbidden substrings json list of strings e.g. `["for","while"]`	remove
Solution visibility	remove
Java imports json list of importables e.g. `["java.util.*"]`	remove
Override Java classname else defaults to websheet name	remove
Dependent on other websheets? json list of websheet names in this folder e.g. `["DataStructure"]`	remove
Is example? i.e., just a demo	remove
Add compiler flag(s) json list of flags e.g. `["-Wno-unused-variable"]`	remove
Remove default compiler flag(s) json list of flags see default_cppflags e.g. `["-Wno-write-strings"]`	remove

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