File I/O

//  File I/O
//  Date : 23.11.19
//  Program will read from a file and add some value to it.
//  Then write it to file again.
#include<iostream>
#include<fstream>
#include<vector>
#include<sstream>
using namespace std;

void mainMenu();
void ShowTheFile();
vector<int> ReadFromFile();
void WriteToFile();
void AddValueToElementOfFile();

void ShowTheFile(){
    //   loop to show the array

    vector<int> inputArray = ReadFromFile();
    if(inputArray.size() == 0){
        cout << "File is empty or not exist.\n";
    }
    else{
        cout << "The file contains : " << endl;
        for(int i : inputArray){
            cout << i << ' ';
        }
        cout << endl << endl;
    }
    mainMenu();
}

vector<int> ReadFromFile(){
    ifstream readFile("file.txt");
    string input;
    vector<int> inputArray;
    //  Loop to read all lines in file
    while(getline(readFile, input)){
        //  separating each word from sentence
        stringstream s(input);
        string number;
        //  Loop to read each word and convert to int value
        while(s >> number){
            int k = stoi(number, nullptr, 10);
            inputArray.push_back(k);
        }
    }
    readFile.close();
    return inputArray;
}

void WriteToFile(){
    ofstream writeFile("file.txt");
    cout << "Enter number of input: ";
    int n; cin >> n;
    for(int i = 0; i < n; i++){
        int k; cin >> k;
        writeFile << k << ' ';
    }
    writeFile.close();
    mainMenu();
}

void AddValueToElementOfFile(){
    vector<int> arrayInFile = ReadFromFile();
    int value;
    cout << "Enter the value to add with the elements of array: ";
    cin >> value;
    for(int i = 0; i < arrayInFile.size(); i++){
        arrayInFile[i] = arrayInFile[i] + value;
    }
    ofstream writeFile("file.txt");
    for(int i: arrayInFile){
        writeFile << i << ' ';
    }
    writeFile.close();
    mainMenu();
}

void mainMenu(){
    cout << "Read from the file: Press '1'" << endl
         << "Take input and write to file: Press '2'" << endl
         << "Take input value and add it to all values in file and the write it back : Press '3'" << endl
         << "Exit : Press '4'" << endl
         << endl
         << "Enter your choice: ";
    int choice; cin >> choice;

    switch(choice){
    case 1:
        ShowTheFile();
        break;
    case 2:
        WriteToFile();
        break;
    case 3:
        AddValueToElementOfFile();
        break;
    case 4:
        return;
        break;
    default:
        break;
    }
}

int main(){
    mainMenu();
}