Reading a file containing characters in parentheses into a vector of integers

Question

I am attempting to read in a file containing characters enclosed in parentheses into a vector of integers.

My text file:

(2 3 4 9 10 14 15 16 17 19)

Heres my code:

#include <iostream>
#include <fstream>
#include <vector>

using namespace std;


int main(){
  ifstream file;
  file.open("moves.txt");

  vector<int> V;
  char c;

  if (file){
    while (file.get(c)){
      if (c != '(' && c != ')' && c != ' ')
        V.push_back(c - '0');
    }
  }
  else{
    cout << "Error openning file." << endl;
  }

  for (int i = 0; i < V.size(); i++)
    cout << V[i] << endl;
}

My Output:

Desired output:

What is causing the separation of two digit numbers and why is there a negative number at the end of my output?

You are reading a character at a time, and converting any non-paren, non-whitespace to a number. Why do you wonder that each character is handled separately? Anyway, take a look at formatted input functions `>>`. — Deduplicator, Nov 29 '14 at 01:57

score 2 · Accepted Answer · edited May 23 '17 at 10:33

Don't read characters one by one : read a line, and parse the numbers within it.

By using the is_number (c++11) function of this answer :

bool is_number(const std::string& s)
{
    return !s.empty() && std::find_if(s.begin(),
        s.end(), [](char c) { return !std::isdigit(c); }) == s.end();
}

You can read line by line with std::getline and then stream the numbers to a std::stringstream. std::stoi can be used to convert a string to an integer :

 std::string line;
 while(std::getline(file, line))
 {
    line.replace(line.begin(), line.begin() + 1, "");
    line.replace(line.end() - 2, line.end() - 1, "");
    std::string numberStr;
    std::stringstream ss(line);
    while (ss >> numberStr){
      if (is_number(numberStr))
        v.push_back(std::stoi(numberStr));
    }
 }

You'd have to make the replace more robust (by checking the presence of parentheses at these positions)

Reading a file containing characters in parentheses into a vector of integers

1 Answers1