C++ Filling out these functions /* input is a collatz map (map >)and a long if t

Question

C++ Filling out these functions

/*

input is a collatz map (map >)and a long

if the number exists as a key in the map

returns the Collatz_to_string of that pair

otw returns an empty string

*/

string sequence_in_map_to_string(map > &m, long number) {

}

/*

input is a collatz map (map >)and a long

returns a vector, the collatz sequence for that number

Operation. As you iterate through the collatz sequence

- uses collatz_next if the element in question is not in the map

- if the element *is* in the map, copies the sequence from the map

to the end of the current sequence and ends.

*/

vector collatz_sequence(map > &m, long number) {

}

/*

input is a collatz map (map >)and a low and high long

fills the map from low to high inclusive with each element's collatz sequence

using the function collatz_sequence

*/

void collatz_range(map > &m, long low, long high) {

}

Explanation / Answer

lab09_fuctions.h

#pragma once

#include<vector>
using std::vector;
#include<string>
using std::string;
#include<map>
using std::map;
#include<utility>
using std::pair;

using Collatz = pair<long, vector<long> >;

long collatz_next(long n);
string Collatz_to_string(const Collatz &p);
string sequence_in_map_to_string(map<long, vector<long> > &m, long number);
vector<long> collatz_sequence(map<long, vector<long> > &m, long number);
void collatz_range(map<long, vector<long> > &m, long low, long high);

Lab08_functions.cpp

#include "stdafx.h"
#include "Lab08_functions.h"
#include <iostream>

int main()
{
    return 0;
}

/**
* gives the next collatz number
*/
long collatz_next(long n)
{
    // if number is 0 or less, throws range_error;
    if (n < 1) { throw std::range_error("Number should be positive (1 or greater)!"); }

    if (n % 2) { return n / 2; }
    else { return 3 * n + 1; }
}

/*
* display format for collatz
*/
string Collatz_to_string(const Collatz & p)
{
    std::string out{};
    // output is a string of the format number :
    out += std::to_string(p.first) + " : ";

    // sequence(comma separated)
    for (int i{ 0 }; i < p.second.size(); ++i)
    {
        out += p.second.at(i) + ", ";
    }

    // ending in 1 no trailing comma
    out += "1";

    return out;
}

string sequence_in_map_to_string(map<long, vector<long>>& m, long number)
{
    // if the number exists as a key in the map
    for (std::map<long, vector<long>>::iterator it = m.begin(); it != m.end(); ++it)
    {
        if (number == it->first) { return Collatz_to_string(*it); }
    }

    return string{};
}

/**
* returns the collatz sequence for that number
*/
vector<long> collatz_sequence(map<long, vector<long>>& m, long number)
{
    Collatz collatz;

    std::map<long, vector<long>>::iterator iterator{ m.find(number) };

    if (iterator != m.end())
    {
        // copies the sequence(collatz?) from the map         
        collatz.first = number;
        collatz.second = iterator->second;

        // to the end of the current sequence and ends.
        m.insert(collatz);
        return iterator->second;
    }

    // only init this vector if seq is not found!
    std::vector<long> collatz_seq{};

    collatz_seq.push_back(number);
    // uses collatz_next if the element in question is not in the map
    while (1)
    {
        number = collatz_next(number);

        if (number < 2) { break; }
        else { collatz_seq.push_back(number); }
    }

    collatz.first = number;
    collatz.second = collatz_seq;
    m.insert(collatz);

    return collatz_seq;
}

/*
* fills the map from low to high inclusive with each element's collatz sequence
* using the function collatz_sequence
*/
void collatz_range(map<long, vector<long>>& m, long low, long high)
{

    for (long i{ low }; i < high + 1; ++i)
    {
        collatz_sequence(m, i);
    }
}

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