Question

This program reads strings of numbers from a txt file, converts them to integers, stores them in a vector, and then tries to output them in an organized fashion like so….

If txt file says:

7 5 5 7 3 117 5

The program outputs:

3
5   3
7   2
117

so if the number occurs more than once it outputs how many times that happens. Here is the code so far.

#include "std_lib_facilities.h"

int str_to_int(string& s)
{
    stringstream ss(s);
    int num;
    ss >> num;
    return num;
}

int main()
{
    cout << "Enter file name.\n";
    string file;
    cin >> file;
    ifstream f(file.c_str(), ios::in);

    string num;
    vector<int> numbers;
    while(f>>num)
    {
        int number = str_to_int(num);
        numbers.push_back(number);
    }

    sort(numbers.begin(), numbers.end());

    for(int i = 0; i < numbers.size(); ++i)
    {
     if(i = 0 && numbers[i]!= numbers[i+1]) cout << numbers[i] << endl;
     if(i!=0 && numbers[i]!= numbers[i-1])
     {
          cout << numbers[i] << '\t' << counter << endl;
          counter = 0;
     }
     else ++counter;
    }
 }

Edit: Program is getting stuck. Looking for an infinite loop right now.

Answer 1

How about using a map, where the key is the number you’re tracking and the value is the number of occurrences?

If you must use a vector, you’ve already got it sorted. So just keep track of the number you previously saw. If it is the same as the current number, increment the counter. Every time the number changes: print out the current number and the count, reset the count, set the last_seen number to the new number.