Swapping Elements

gistfile1.cpp

#include <iostream>
#include <fstream>
#include <sstream>
#include <string>
#include <vector>
using namespace std;

/// Recieves input in the form of 22 16 1 44 72 42 92 87 59 93 87 41 : 3-12, 0-1, 5-12
/// The numbers after the colon on instructions. i.e swap elements in places 3 and 12,then 0 and 1 and so on.
/// Program takes in file for instruction. Parses string into a number array and instructions
/// Parses the instructions and loops through swapping elements then loops through and prints array.
/// I keep everything as as a string until I need to learn its number to know which element to access

template <typename T>
T convertToInt(const string &text)
{
    stringstream ss_(text);
    T result;
    return ss_ >> result ? result : 0;
}


/// Inputs a string and parses it into two arrays, number array and the instruction
void parseString(vector<string> &numArray, vector<string> &instructArray, const string &text)
{
    size_t positionColon = text.find_first_of(":", 0);
    string array_ = text.substr(0, positionColon);
    string instructions_ = text.substr(positionColon+1, string::npos);
    size_t prevPos = 0, pos;
    /// Parse through each space and grab the number
    while((pos = array_.find_first_of(" ", prevPos)) != string::npos )
    {
        if( pos > prevPos)
          numArray.push_back(array_.substr(prevPos, pos-prevPos));
        prevPos = pos + 1;
    }
    if ( prevPos < array_.length()  )
        numArray.push_back(array_.substr(prevPos, string::npos));

    // Repeat search now on instruction array
    prevPos = 0;
    while( (pos = instructions_.find_first_of(",", prevPos)) != string::npos )
    {
       if( pos > prevPos  )
           instructArray.push_back(instructions_.substr(prevPos, pos-prevPos));
       prevPos = pos + 1;
    }
    if(prevPos < instructions_.length())
        instructArray.push_back(instructions_.substr(prevPos, string::npos));
}

/// Grab instruction string, first instruction found after the space. second instruction found
/// after the dash.  Convert these to int's as we need the number and then store as ints
void parseInstructions(const string &instruction, int &a, int &b)
{
    size_t firstPos, secondPos;

    firstPos = instruction.find_first_of(" ", 0);
    secondPos = instruction.find_first_of("-", 0);

    a = convertToInt<int>(instruction.substr(firstPos, secondPos));
    b = convertToInt<int>(instruction.substr(secondPos+1, string::npos));
}

int main(int argc, char *argv[])
{
    fstream inputFile(argv[1]);
    string line;
    vector<string> numArray;
    vector<string> instructArray;
    int a;
    int b;
    string temp;
    while(getline(inputFile, line))
    {
        /// Parse entire line to create a number array and an instruction array
        parseString(numArray, instructArray, line);
        
        /// Cycle through each instruction string and extract the element positions in the swap
        /// Then follow those instructions in swapping
        for(int i = 0; i < instructArray.size(); ++i)
        {
          parseInstructions(instructArray[i], a, b);
          temp = numArray[a];
          numArray[a] = numArray[b];
          numArray[b] = temp;

        }
        /// Print post-swapped number array
        for(int i = 0; i <numArray.size(); ++i)
        {
           cout << numArray[i] << " ";
        }
        cout << endl;
        numArray.clear();
        instructArray.clear();
    }
   return 0;
}