C++ String Exercises: Convert a given non-negative integer to English words

C++ String: Exercise-15 with Solution

Write a C++ program to convert a given non-negative integer into English words.

Sample Solution:

C++ Code :

#include <stdlib.h> // Standard library for general functions in C
#include <iostream> // Input/output stream library
#include <string> // String operations library
#include <vector> // Vector container library for dynamic arrays

using namespace std; // Using the standard namespace

static string belowTwenty[] = {"Zero", "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine",
                                "Ten", "Eleven", "Twelve", "Thirteen", "Fourteen", "Fifteen", "Sixteen", 
                                "Seventeen", "Eighteen", "Nineteen"};

static string belowHundred[] = {"", "", "Twenty", "Thirty", "Forty", "Fifty", "Sixty", "Seventy", "Eighty", "Ninety"};

static string overThousand[] = {"Hundred", "Thousand", "Million", "Billion"};

// Function to convert numbers below 100 into words
string number_to_words_below_hundred(long long int num) {
    string result;

    // Handling the cases for numbers below 20, between 20 and 99, and numbers greater than or equal to 100
    if (num == 0) {
        return result;
    } else if (num < 20) {
        return belowTwenty[num];
    } else if (num < 100) {
        result = belowHundred[num / 10];
        if (num % 10 > 0) {
            result += " " + belowTwenty[num % 10];
        }
    } else {
        result = belowTwenty[num / 100] + " " + overThousand[0];
        if (num % 100 > 0) {
            result += " " + number_to_words_below_hundred(num % 100);
        }
    }
    return result;
}

// Function to convert numbers into words
string number_to_words(int num) {
    if (num == 0) return belowTwenty[num];

    vector<string> ret;

    // Loop to convert the number into words based on groups of thousands
    for (; num > 0; num /= 1000) {
        ret.push_back(number_to_words_below_hundred(num % 1000));
    }

    string result = ret[0];

    // Concatenating the words and digits according to their positions
    for (int i = 1; i < ret.size(); i++) {
        if (ret[i].size() > 0) {
            if (result.size() > 0) {
                result = ret[i] + " " + overThousand[i] + " " + result;
            } else {
                result = ret[i] + " " + overThousand[i];
            }
        }
    }
    return result;
}

// Main function
int main() {

    // Printing numbers and their word representation
    long long int num = 0;
    cout << num << " ->  " << number_to_words(num) <<  endl;
    num = 9;
    cout << "\n" << num << " ->  " << number_to_words(num) <<  endl;
    // More test cases...
    // ...
    return 0; // Return 0 to indicate successful completion
}

Sample Output:

0 ->  Zero

9 ->  Nine

12 ->  Twelve

29 ->  Twenty Nine

234 ->  Two Hundred Thirty Four

777 ->  Seven Hundred Seventy Seven

1023 ->  One Thousand Twenty Three

45321 ->  Forty Five Thousand Three Hundred Twenty One

876543 ->  Eight Hundred Seventy Six Thousand Five Hundred Forty Three

8734210 ->  Eight Million Seven Hundred Thirty Four Thousand Two Hundred Ten

329876120 ->  Three Hundred Twenty Nine Million Eight Hundred Seventy Six Thousand One Hundred Twenty

18348797629876120 ->  One Billion Five Hundred Fifty Six Million Six Hundred Sixty Two Thousand One Hundred Sixty Eight

Flowchart:

C++ Code Editor:

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Previous C++ Exercise: Find the numbers in a string and calculate the sum.