Question

The following are questions from a study guide, could I get some good examples of c++ code with comments for a better understanding, thanks!

2.Be prepared to implement a stack, queue, or priority queue using a linked list (singly or doubly linked).

3.Be prepared to implement a “weird” method that you’ve never heard of before to prove you truly understand what you are doing.  Here is an example:

a.Implement ‘void decimate()’ which deletes every 10^th item from the list: https://en.wikipedia.org/wiki/Decimation_(Roman_army)

Recurison:

4.Write a recursive function ‘int threeSum(int n)’ that returns the sum of 1+2+3+4+…+3*n.  (no loops!).  

5.Write a method that ‘int numThrees(int n)’ that returns the number of 3’s in the base 7 expansion of n.

Answer 1

Hi friend, As per the HomeworkLib policy, please post one question per post.

I have answered Q4.

4.Write a recursive function ‘int threeSum(int n)’ that returns the sum of 1+2+3+4+…+3*n.  (no loops!).  

#include <iostream>

using namespace std;

// function prototype

int threeSum(int n);

int threeSumHelper(int n);

int threeSum(int n) {

return threeSumHelper(3*n);

}

int threeSumHelper(int n) {

if(n == 1)

return 1;

return n + threeSumHelper(n-1);

}

int main() {

int n;

cout<<"Enter the value of n: ";

cin>>n;

cout<<"threeSum("<<n<<"): "<<threeSum(n)<<endl;

return 0;

}

secondweek → secondweek secondweek g++ threesum . cpp secondweek/a.out Enter the value of n: 7 threeSum(7): 231 secondweek

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