Question

Write a C++ or program that parses (and stores into a variable of the correct type) a string into 4 fields separated by a colon (:):

Field 1: A non-empty string value that does not contain a colon
Filed 2: An odd integer, or empty
Filed 3: One of these values: red, orange, yellow, green, blue, indigo, violet
Field 4: Another string value (may contain colon characters)

output:

Accept: sample:556989:green:Longer example string :)
Reject (bad color): sample:556989:purple:Longer example string :)

A sample string is:
sample:556989:green:Longer example string :)
The main method should read sample strings, one line at a time, from a file specified on the command line (i.e., passed in via argv)

Answer 1

Code in C++

#include<iostream>
#include<math.h>
#include <fstream>
using namespace std;

int main(int argc, char const *argv[])
{
        //handle less arguments
        if(argc<2){
                cout<<"Please enter the input file in command line arguments"<<endl;
                return 0;
        }
        
        //use ifstream to parse the file
        ifstream infile(argv[1]);

        string line;
        //read line by line form the file
        while (std::getline(infile, line))
        {
                string non_empty_string="", color="", final_string;
                int val=0;
                int i=0;
                //read non_empty_string
                while(line[i]!=':'){
                        non_empty_string+=line[i];
                        i++;
                }
                i++;
                //check for empty integer
                if(line[i]==':'){
                        val=-1;//we set this to -1 to indicate empty value
                }
                //read the integer
                while(line[i]!=':'){
                        val=val*10+(line[i]-'0');
                        i++;
                }
                i++;
                //read the color
                while(line[i]!=':'){
                        color+=line[i];
                        i++;
                }
                i++;
                //final string is the remaing part of the line
                final_string = line.substr(i);
                //chaeck for accept and reject
                if(non_empty_string.size()>0 && (val==-1 || val%2==1) && 
                        (color=="red" || color=="orange" || color=="yellow" || color=="green" || color=="blue" || color=="indigo" || color=="violet")){
                                printf("Accept: %s\n", line.c_str());
                }else{
                        if(non_empty_string.size()==0){
                                printf("Reject: (first field should be non-empty string without colon): %s\n", line.c_str());
                        }else if(val!=-1 && val%2==0){
                                printf("Reject: (integer should be odd or empty): %s\n", line.c_str());
                        }else{
                                printf("Reject: (bad color): %s\n", line.c_str());
                        }
                }
        }
        return 0;
}

Sample Input/Output

Content in input.txt

Console Input/output