Interactive problems in competitive programming often require manual interaction to test the correctness of the solution. While writing the checker program is usually straightforward, connecting the checker program with the solution program can be challenging. This blog post introduces a simple Linux terminal setup that makes this connection easy, eliminating the need for manual input during testing.

There are other solutions to this, the one over here uses croupier(a python program) to make the two interact.

Simplifying the Connection with Linux Terminal: The Linux terminal provides powerful tools to simplify the testing process for interactive problems. By leveraging a bash script and named pipes, you can effortlessly connect the solution program with the checker program. Here's a script:

sol=$1
checker=$2

mkfifo pipe_in pipe_out

./$sol < pipe_in 2> error.log  | tee pipe_out &
./$checker < pipe_out | tee pipe_in 

echo "------------------- Error ------------------"
cat error.log
rm error.log
rm pipe_in
rm pipe_out

Save this by the name (say) run_checker.sh. Then run the following commands.

Compile the solution and checker programs. g++ -o E E.cpp g++ -o E_checker E_checker.cpp

Make the script executable

chmod +x run_checker.sh

Run the script with executable solution filename as first argument and executable checker filename as second argument. ./run_checker.sh E E_checker

Here E.cpp contains your solution program and E_checker.cpp contains your checker program.