Dynamic Programming Coin Change Problem

I am having an issue with my coin change program. The idea behind the program is to take input from a text file which will be coin values and an amount and fine the lowest number of coins of the given domination to make that amount. For example:
1 2 5
10
1 3 7 12
29

This would return the following in a text file:
1 2 5
10
0 0 2
2
1 3 7 12
29
0 1 2 1
4

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   #include <iostream>
#include <string>
#include <vector>
#include <cmath>
#include <fstream>
#include <array>

using namespace std;

//function to convert string to int vector

vector<int> list_from_string(string len) {



	string x = "";

	vector<int> vec;

	for (int i = 0; i <= len.length(); i++) {



		if (i == len.length() || len[i] == ' ') {

			//stoi function used to convert string to int

			vec.push_back(stoi(x));

			x = "";

		}
		else {

			//appending chars to string

			x = x + len[i];

		}

	}

	return vec;

}

//function to calculate change from denom and coins

vector<int> calculate(vector<int> denom, int coins) {

	//creating a 2d bool array

	bool arr[coins + 1][denom.size() + 1]; //issue here

	//setting all values to false

	for (int i = 0; i <= coins; i++) {

		for (int j = 0; j <= denom.size(); j++) {

			arr[i][j] = false;

		}

	}

	//setting values with 0 coins to true

	for (int i = 0; i <= denom.size(); i++) {

		arr[0][i] = true;

	}

	//filling array using dynamic programming

	for (int i = 1; i <= coins; i++) {

		for (int j = 1; j <= denom.size(); j++) {

			if (i >= denom[j - 1]) {

				arr[i][j] = arr[i][j] || arr[i - denom[j - 1]][j] || arr[i - denom[j - 1]][j - 1];

			}

		}

	}

	int x = coins; int y = denom.size();

	//creating resulting vector

	vector<int> ans;

	for (int i = 0; i<denom.size(); i++) { ans.push_back(0); }

	//filling vector using backtracking

	while (x>0 && y>0) {

		if (arr[x - denom[y - 1]][y]) {

			ans[y - 1]++;

			x = x - denom[y - 1];

		}
		else if (arr[x - denom[y - 1]][y - 1]) {

			ans[y - 1]++;

			x = x - denom[y - 1];

			y--;

		}
		else {

			y--;

		}

	}

	//returning the vector

	return ans;

}

int main() {



	//ifstream object to read amount.txt to take as input

	ifstream infile("amount.txt");

	string str;

	//denom vector to store denominators in a vector

	vector<int> denom;

	//a flag variable to read denominators first then coins second.

	int flag = 0;

	//ofstream object to write output to change.txt

	ofstream myfile;

	myfile.open("change.txt");

	//while loop to read lines of amount.txt

	while (getline(infile, str)) {



		//if flag is 0 then denominators are read

		//else if flag is 1 then no of coins are read



		if (flag == 0) {



			//function to convert string to int vector

			denom = list_from_string(str);



			//writing vector to change.txt file

			for (int i = 0; i<denom.size(); i++) {

				myfile << denom[i] << " ";

			}

			myfile << "\n";



			//setting flag to 1 to read no of coins

			flag = 1;



		}
		else {



			//stoi is used to convert string to integer

			int coins = stoi(str);

			//writing coins to change.txt file

			myfile << coins << "\n";

			//function to convert vector and coins to change vector

			vector<int> change = calculate(denom, coins);

			//writing change vector to change.txt file and calculating no of coins

			int no = 0;

			for (int i = 0; i<change.size(); i++) {

				myfile << change[i] << " ";

				no = no + change[i];

			}

			//writing no of coins to change.txt

			myfile << "\n";

			myfile << no << "\n";

			//setting flag to 0 again

			flag = 0;

		}

	}

	return 0;

}


When I go to try and make a 2D array of bools using this: bool arr[coins + 1][denom.size() + 1], my IDE is causing an error to be thrown. Any advice or guidance would be appreciated.
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#include <fstream>
#include <string>
#include <vector>

//function to convert string to int vector
std::vector<int> list_from_string(const std::string& list);
//function to calculate change from denom and coins
std::vector<int> calculate(const std::vector<int>& denom, int amount);

int main()
{
    std::ifstream infile("amount.txt");
    bool flag { true };             // denominations first, then amount.
    std::ofstream outfile("change.txt");
    std::vector<int> denom; // denominations (must endure two iterations!)
    for (std::string str; getline(infile, str); /**/) {
        if (flag) {
            denom = list_from_string(str);
            for (std::size_t i = 0; i < denom.size(); i++) {
                outfile << denom.at(i) << ' ';
            }
            outfile << '\n';
            flag = false;   //  at next iteration read the amount!
        }
        else {
            int amount = std::stoi(str);
            outfile << amount << '\n';
            std::vector<int> change = calculate(denom, amount);
            int no = 0;
            for (std::size_t i = 0; i<change.size(); i++) {
                outfile << change[i] << ' ';
                no +=  change[i];
            }
            outfile << '\n' << no << '\n';
            denom.clear();
            flag = true;    // at next iteration read the denominations list!
        }
    }
    return 0;
}

std::vector<int> list_from_string(const std::string& list)
{
    std::string x;
    std::vector<int> vec;
    for (std::size_t i = 0; i <= list.length(); i++) {
        if (i == list.length() || list.at(i) == ' ') {
            vec.push_back(std::stoi(x));
            x.clear();
        }
        else {
            x += list.at(i);
        }
    }
    return vec;
}

std::vector<int> calculate(const std::vector<int>& denom, int coins)
{
    bool** arr = new bool*[coins + 1];
    for(int i {}; i < coins + 1; ++i) { arr[i] = new bool[denom.size() + 1] { false }; }

    //setting values with 0 coins to true
    for (std::size_t i = 0; i <= denom.size(); i++) {
        arr[0][i] = true;
    }

    //filling array using dynamic programming
    for (int i = 1; i <= coins; i++) {
        for (std::size_t j = 1; j <= denom.size(); j++) {
            if (i >= denom[j - 1]) {
                arr[i][j] =    arr[i][j]
                            || arr[i - denom[j - 1]][j]
                            || arr[i - denom[j - 1]][j - 1];
            }
        }
    }

    int x = coins, y = denom.size();

    //creating resulting vector
    std::vector<int> ans (denom.size());

    //filling vector using backtracking
    while (x > 0 && y > 0) {
        if (arr[x - denom[y - 1]][y]) {
            ans[y - 1]++;
            x = x - denom[y - 1];
        }
        else if (arr[x - denom[y - 1]][y - 1]) {
            ans[y - 1]++;
            x = x - denom[y - 1];
            y--;
        }
        else {
            y--;
        }
    }
    for(int i {}; i < coins + 1; ++i) { delete[] arr[i]; }
    delete[] arr;
    return ans;
}

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