Convert Array of Integers to Comma-Separated String

Given an array of integers arr[] of size N, return the string representation of integers separated by comma and a space. The last element should be separated by " and ", instead of comma and a space.

Examples:

Input : arr=[10, 20, 30, 40, 50]
Output: "10, 20, 30, 40 and 50"

Input: arr = [2,5]
Output : "2 and 5"

Input: arr = [10]
Output: "10"

Approach: The problem can be solved by using the following approach:

Iterate through the input array and for every integer, convert it to string and append it to the answer string. For every integer, check:

• If the current integer is the last element of the array move out of the loop
• If the current integer is the second last element of array, then append " and " to the answer.
• Else, append a comma and a space to the answer.

After all the iterations return the answer string.

Steps to solve the problem:

• Maintain a string answer to store the final result
• Iterate a loop from 0 to N - 1:
  • Convert arr[i] to string and append to answer string
  • If i < N - 2, answer = answer + ", "
  • If i == N-2, answer = answer + " and "
• Return answer

Below is the implementation of the approach:

#include <iostream>
#include <vector>
using namespace std;

// Method to convert array to string
string arrayToString(vector<int>& arr) {
    // Variable to store the answer
    string answer;
    int N = arr.size();
    // Iterate over all the elements in arr[]
    for (int i = 0; i < N; i++) {
        answer += to_string(arr[i]);
        if (i < N - 2) {
            answer += ", ";
        } else if (i == N - 2) {
            answer += " and ";
        }
    }
    return answer;
}

int main() {
    vector<int> arr = {10, 20, 30, 40, 50};
    cout << arrayToString(arr) << endl;
    arr = {2, 5};
    cout << arrayToString(arr) << endl;
    arr = {10};
    cout << arrayToString(arr) << endl;
    return 0;
}

// Java implementation for the approach

import java.util.ArrayList;
import java.util.List;

public class Main {
    // Method to convert array to string
    public static String arrayToString(List<Integer> arr) {
        // Variable to store the answer
        StringBuilder answer = new StringBuilder();
        int N = arr.size();
        // Iterate over all the elements in arr[]
        for (int i = 0; i < N; i++) {
            answer.append(arr.get(i));
            if (i < N - 2) {
                answer.append(", ");
            } else if (i == N - 2) {
                answer.append(" and ");
            }
        }
        return answer.toString();
    }

    public static void main(String[] args) {
        List<Integer> arr = new ArrayList<>();
        arr.add(10);
        arr.add(20);
        arr.add(30);
        arr.add(40);
        arr.add(50);
        System.out.println(arrayToString(arr));

        arr = new ArrayList<>();
        arr.add(2);
        arr.add(5);
        System.out.println(arrayToString(arr));

        arr = new ArrayList<>();
        arr.add(10);
        System.out.println(arrayToString(arr));
    }
}

# Function to convert a list to a formatted string
def list_to_string(lst):
    # Variable to store the answer
    answer = ""
    N = len(lst)
    
    # Iterate over all the elements in the list
    for i in range(N):
        answer += str(lst[i])
        
        if i < N - 2:
            answer += ", "
        elif i == N - 2:
            answer += " and "
    
    return answer

if __name__ == "__main__":
    arr = [10, 20, 30, 40, 50]
    print(list_to_string(arr))
    
    arr = [2, 5]
    print(list_to_string(arr))
    
    arr = [10]
    print(list_to_string(arr))

using System;
using System.Collections.Generic;

public class GFG {
    // Method to convert list to string
    public static string ListToString(List<int> arr)
    {
        // Variable to store the answer
        var answer = new System.Text.StringBuilder();
        int N = arr.Count;
        // Iterate over all the elements in arr[]
        for (int i = 0; i < N; i++) {
            answer.Append(arr[i]);
            if (i < N - 2) {
                answer.Append(", ");
            }
            else if (i == N - 2) {
                answer.Append(" and ");
            }
        }
        return answer.ToString();
    }

    public static void Main(string[] args)
    {
        List<int> arr = new List<int>{ 10, 20, 30, 40, 50 };
        Console.WriteLine(ListToString(arr));

        arr = new List<int>{ 2, 5 };
        Console.WriteLine(ListToString(arr));

        arr = new List<int>{ 10 };
        Console.WriteLine(ListToString(arr));
    }
}

// Method to convert array to string
function arrayToString(arr) {
    // Variable to store the answer
    let answer = "";
    const N = arr.length;
    
    // Iterate over all the elements in arr[]
    for (let i = 0; i < N; i++) {
        answer += arr[i].toString();
        
        if (i < N - 2) {
            answer += ", ";
        } else if (i === N - 2) {
            answer += " and ";
        }
    }
    return answer;
}

// Main function
function main() {
    let arr = [10, 20, 30, 40, 50];
    console.log(arrayToString(arr));

    arr = [2, 5];
    console.log(arrayToString(arr));

    arr = [10];
    console.log(arrayToString(arr));
}

// Run the main function
main();

10, 20, 30, 40 and 50
2 and 5
10

Time Complexity: O(N), where N is the size of input array
Auxiliary Space: O(1)