// [email protected]
// demo: sum of elements in range, validation
// 2026-03-05
// tested on Win with g++



// oldschool
#include <cstdlib>
#include <cstdio>
#include <ctime>
// error handling
#include <exception>
#include <stdexcept>
// I/O handling
#include <iostream>
#include <sstream>
// containers
#include <vector>


// configuration
#define LOW 10
#define HIGH 99
#define MAX_SIZE 1000

#define COLUMNS 20

using namespace std;






// value in [low; high] or invalid_argument thrown
void validateRange(int value, int low, int high){
    if(value < low || value > high)
        throw invalid_argument(string("Value in [") + to_string(low) + "; " + to_string(high) + "] required");
}

// stream clean or invalid_argument thrown
void validateStream(istream &in){
    if(in.fail()){
        in.clear();
        in.ignore(256, '\n');
        throw invalid_argument("Bad input!");
    }
}



// vector with n random elements in [LOW; HIGH]
vector<int> generate(unsigned n){
    validateRange(n, 1, MAX_SIZE);
    vector<int> v;
    for(int i = 0; i < n; ++i)
        v.push_back(LOW+rand()%(HIGH-LOW+1));
    return v;
}

// data to stdout
void print(vector<int> data){
    cout << "Data: ";
    for(int i = 0; i < data.size(); ++i){
        if(i % COLUMNS == 0)
            cout << endl;
        cout << data[i] << " ";
    }
    cout << endl;
}



// sum all from data[a] to data[b]
int computeSum(vector<int> data, int a, int b){
    validateRange(a, 1, data.size());
    validateRange(b, 1, data.size());
    int sum = 0;
    for(int i = a; i <= b; ++i){
        sum += data[i-1];
    }
    return sum;
}



int main(){
    try {
        // init
        srand(time(NULL));

        // continue computations
        while(1){
            try {
                // input size and range for sum
                int n = 0, a = 0, b = 0;
                cout << "Enter size n and range [a; b] all in [1; " << MAX_SIZE << "]: ";
                cin >> n >> a >> b;
                //cout << cin.good() << cin.fail() << cin.bad() << cin.eof() << endl;
                validateStream(cin); // throws if invalid

                // proceed to computations
                vector<int> v = generate(n);
                print(v);
                int sum = computeSum(v, a, b); // may throw, try before printing
                cout << "Sum: " << sum << endl;

            } catch (invalid_argument& e){
                cout << e.what() << endl;
            }
        }
    } catch(...){ // should never happen
        cout << "Uncaught exception!" << endl;
    }
    return 0;
}