Code after my for loop won't work, the print statement after the for loop does not get printed

Question

My code does not continue after the for loop, the cursor just remains there blinking. I tried it on multiple compilers still same problem.

   Input:
   3 50
   60 20
   100 50
   120 30

when I give this input it take 3 values, than does not print the statement after the for loop. It just pauses. :(

here is the for loop (image)

This is the problem I face. not working after taking input (image)

Here is my code.

#include <iostream>
#include <vector>
#include <algorithm>

using std::vector;

double get_optimal_value (int capacity, vector<int> weights, 
                              vector<int> values, int n){
    std::cout<<"we are in the function";
    double value = 0.0;
    int current_weight = 0;

    vector<double> v_by_w(n);
    for (int i = 0; i < n; ++i)
        v_by_w[i] = values[i] / weights[i];

    std::cout<<"printing the v/w elements";
    for (int i = 0; i < n; ++i)
        std::cout<< v_by_w[i] << " ";

    while( current_weight < capacity ) {
        int maxi = std::max_element(v_by_w.begin(),v_by_w.end()) - 
        v_by_w.begin();

        if((capacity - current_weight) > weights[maxi]){
            current_weight += weights[maxi];
            value = values[maxi];
        } else
            value += v_by_w[maxi]*(capacity - current_weight);

        v_by_w[maxi] = -1;
    }

    return value;
}

int main() {
    int n;
    int capacity;
    char ch;
    std::cin >> n >> capacity;
    vector<int> values(n);
    vector<int> weights(n);
    for (int i = 0; i < n; i++) {
        std::cout<<"hello "<<i ;
        std::cin >> values[i] >> weights[i];
    }

    std::cout<<"we took the values"; //why won't this print?

    double optimal_value = get_optimal_value(capacity, weights, values, n);

    std::cout.precision(10);
    std::cout << optimal_value << std::endl;

    return 0;
}

My goal is to print that we took the input after taking the input.

please let me know why does this happen. What can I do to prevent it.

This will really help me :)

Answer 1

I tried running your code below:

int main()
{
int n;
int capacity;
char ch;
std::cin >> n >> capacity;
vector<int> values(n);
vector<int> weights(n);
for (int i = 0; i < n; i++) {
    std::cout<<"hello "<<i ;
    std::cin >> values[i] >> weights[i];
}

std::cout<<"we took the values"; //this is getting printed after taking 2n input from keyboard
}

Below is a explanation of sample run of your program:

On running the code, I get empty console window. At this point, the line below is expecting two input from the keyboard: std::cin >> n >> capacity; So I give the below input(2 space 3 enter) 2 3 // please note with this input 2 is assigned to variable n and 3 is assigned to variable capacity

Now the program execution control enters your for-loop and print the line below code: std::cout<<"hello "<

output hello 0 Now enter your two input:output hello 011 12 (11 space 12 enter) // after hitting enter 11 is assigned to values[0] and 12 is assigned to weights[0]

this triggers next iteration of loop, console window looks as shown below:

hello 011 12 hello 1 now enter your two input:hello 113 14(13 space 14 enter) // after hitting enter 13 is assigned to values[1] and 14 is assigned to weights[1]

Now loop is terminated and your text after loop is print on the screen.

Catch here is each iteration of for-loop requires two int input from console (std::cin >> values[i] >> weights[i];)