How to read such inputs ? A,1,BC,2

Question

I've started working on hackerrank/hackerearth like sites. There i've found one problem fetching input. Its easy in Java.

Consider a very simple problem of reading input and displaying it : Flow is like :

read A
repeat A times
      read X1,N1,X2,N2 ; where Xi is any string, Ni is any integer.
      display X1+X2, N1+N2

i don't know how to read X1,N1,X2,N2 where X1 and X2 are strings, i've also tried but problem is that when i read first string it reads entire line for eg when i read string it supposed to be X1 but it is X1,N1,X2,N2. code that i used is

scanf("%s,%d,%s,%d", x1, &n1, x2, &n2)

thanks in advance and sorry for my bad english.

Update#1:

example lines :

3
some,123,thing,456
something,579
a,1,b,2
ab,3
hello,100,world,100
helloworld,200

[Find a good beginners C++ book](http://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list), it will tell you how to read input of any type. — Some programmer dude, Apr 04 '17 at 09:02
Look into [std::cin](http://en.cppreference.com/w/cpp/io/cin). — pingul, Apr 04 '17 at 09:03
The reference is there. If you provide an example line you would like to read, then it might be possible to help you more. — pingul, Apr 04 '17 at 09:06
@pingul ok let me edit question for example lines. wait. thanks — Mohan Sharma, Apr 04 '17 at 09:08
You might also want to take a look at the `getdelim()` function: It reads input up to a given delimiter character, and returns it as a C string, allocating memory for it to fit. Seems to be POSIX-2008, by the look of its `man` page. — cmaster - reinstate monica, Apr 04 '17 at 09:13
@cmaster ohh its sound interesting... i'm reading docs of it wait. — Mohan Sharma, Apr 04 '17 at 09:15
`somethng,579` has only one pair of string/integer. This does not conform to your pseudo-code, does it? — Jonathan H, Apr 04 '17 at 09:16
@Sheljohn its exactly as psuedo code. "something,579" is display line of psuedo code after reading "some,123,thing,456". — Mohan Sharma, Apr 04 '17 at 09:18
@Sheljohn "some,123,thing,456" => some+thing=something,123+456=579 => "something,579" — Mohan Sharma, Apr 04 '17 at 09:19
@MohanSharma My mistake, I thought we were parsing from a file here :) — Jonathan H, Apr 04 '17 at 09:21

score 2 · Answer 1 · edited May 23 '17 at 10:30

2

I think you are looking for something like this:

int number_of_inputs;
std::cin >> number_of_inputs;
for (int iteration = 0; iteration < number_of_inputs; ++iteration){
    int integer1, integer2;
    string string1, string2, stupid_comma;
    std::cin >> string1 >> stupid_comma >> integer1 >> stupid_comma >> string2 >> stupid_comma >> integer2;
    std::cout << string1 << " + " << string2 << " = " << integer1+integer2 << std::endl; 
}

edit2: After op provides input, my code is not correct. Check this answer: Parsing a comma-delimited std::string

edit3: alternative split method op requires:

std::vector<std::string> split(const std::string &text, char sep, int num)
{
    std::vector<std::string> tokens;
    std::size_t start = 0, end = 0;
    int elements = 0;

    while ((end = text.find(sep, start)) != std::string::npos) {
        if ( elements == num) break;

        tokens.push_back(text.substr(start, end - start));
        start = end + 1;
        elements++;
    }

    tokens.push_back(text.substr(start));
    return tokens;
}

edit4: new code using split function:

int number_of_inputs;
std::cin >> number_of_inputs;
for (int iteration = 0; iteration < number_of_inputs; ++iteration){
    std:string line;
    cin >> line;
    int integer1, integer2;
    string string1, string2, stupid_comma;
    std::vector<std::string> my_line = split(line, ',', 4);
    string1 = my_line[0];
    string2 = my_line[2];
    integer1 = stoll(my_line[1], nullptr, 10);
    integer2 = stoll(my_line[3], nullptr, 10);
    std::cout << string1 << " + " << string2 << " = " << integer1+integer2 << std::endl; 
}

edited May 23 '17 at 10:30

Community

1
1

answered Apr 04 '17 at 09:07

tknbr

139
1
13

1

i think this code doesn't considering comma. if it is then how ? please clarify. – Mohan Sharma Apr 04 '17 at 09:08
just add an auxiliar string and read the comma with this auxiliar string. This is just an skeleton to help you. – tknbr Apr 04 '17 at 09:09
@MohanSharma is comma used in strings, or numbers? Because if we talk about numbers then it's not an integer, but a float type. – mutantkeyboard Apr 04 '17 at 09:09
I thought he was refearing to a comma to separate input – tknbr Apr 04 '17 at 09:10
@tknbr please see examples lines. let me know if you need more inputs from my side. – Mohan Sharma Apr 04 '17 at 09:11
ok, @MohanSharma is obviously talking about integers. As I have said, the only thing you need to add to my code is an auxiliar string to read the commas and discard them. Just follow the basic code I have provided you. – tknbr Apr 04 '17 at 09:13
@tknbr can you please give an example of code you're thinking right now ? it will helpful – Mohan Sharma Apr 04 '17 at 09:14
@MohanSharma does this help? – tknbr Apr 04 '17 at 09:19
He wants to read alternating strings and integers, which are separated by commas. Afaik, if you stream `cin` into a string, it will gobble up the terminating comma, and, provided that there is no space following, will proceed to read the digits of the following integer, the next comma, etc. until it hits some whitespace. If you don't provide a way to tell the input stream to break input at a comma, your answer is unfortunately useless. – cmaster - reinstate monica Apr 04 '17 at 09:19
@cmaster its to me or tknbr ? – Mohan Sharma Apr 04 '17 at 09:20
@tknbr please run your code and see that string1 itself consume whole line. – Mohan Sharma Apr 04 '17 at 09:21
@MohanSharma That comment was for tknbr. And now tknbr seems to have addressed the comma issue :-) – cmaster - reinstate monica Apr 04 '17 at 09:25
@tknbr hmm... logic seems to java like... reading whole line and splitting by comma and all that... thanks let me run that also and confirm it. – Mohan Sharma Apr 04 '17 at 09:26
@tknbr it is showing error wiz `‘std::__cxx11::string {aka class std::__cxx11::basic_string}’ has no member named ‘split’` – Mohan Sharma Apr 04 '17 at 09:28
@tknbr i think for `split` function to be there, we must include some specific string related library.. which library you use there ? – Mohan Sharma Apr 04 '17 at 09:29
yep, sorry, that was my fault. – tknbr Apr 04 '17 at 09:30
@tknbr sorry to say but that edit#2 answer is also not working :(( – Mohan Sharma Apr 04 '17 at 09:32
@tknbr but inspired from you to find alternative of `split` in c++. i'm searching that – Mohan Sharma Apr 04 '17 at 09:32
You can use the split method I provided. – tknbr Apr 04 '17 at 09:35
@tknbr thanks for split function and it is working. now i need to parse at(1) and at(3) of vector as integer and print output. – Mohan Sharma Apr 04 '17 at 09:37
You can use the function stoll (http://www.cplusplus.com/reference/string/stoll/) to parse strings to integers – tknbr Apr 04 '17 at 09:38
@tknbr can you please use your `split` function into your first code area so i can accept your post as a answer to complete it. i'm not able to edit your things :( – Mohan Sharma Apr 04 '17 at 09:40

score 1 · Accepted Answer · answered Apr 04 '17 at 14:03

Here is a solution using std::regex, even though it is longer than the accepted answer, I find it much clearer and more flexible.

#include <iostream>
#include <string>
#include <regex>

using namespace std;

struct MyPair {
    string x; int n;

    MyPair() {}
    MyPair( const string& x, int n )
        : x(x), n(n) {}
};

void parse_line( const string& str, MyPair& p1, MyPair& p2 ) {

    typedef regex_iterator<string::const_iterator> re_iterator;
    typedef re_iterator::value_type re_iterated;

    regex re("(\\w+),(\\d+),(\\w+),(\\d+)");
    re_iterator rit( str.begin(), str.end(), re );
    re_iterator rend;

    if ( rit != rend ) {
        p1 = MyPair( (*rit)[1], stoi((*rit)[2]) );
        p2 = MyPair( (*rit)[3], stoi((*rit)[4]) );
    }

}

int main() {

    int A = 0;
    while ( A <= 0 ) {
        cin >> A;
    }

    string line;
    MyPair p1, p2;

    for ( int i = 0; i < A; i++ ) {
        cin >> line;
        parse_line( line, p1, p2 );
        cout << (p1.x + p2.x) << " " << (p1.n + p2.n) << endl;
    }

}

Note that it uses features from C++11, so in order to compile it using clang++ (for instance), you should do:

clang++ -std=c++11 file.cpp -o file

Thank you, i always learn different things from different answer, so it doesn't matter how long is your code while learning. What i learn from your code is how to use regex in c++. so thanks. but i'm not able grasp first loop in main function. whats the purpose of that loop in main ? — Mohan Sharma, Apr 04 '17 at 14:28
ohh gotcha.. you're trying to repeat asking procedure until A>0. got it. — Mohan Sharma, Apr 04 '17 at 14:29

How to read such inputs ? A,1,BC,2

2 Answers2