How to test your solution in Competitive Programming, on Linux?

I'm known as Errichto. I compete in and organize programming competitions. I'm a finalist of ACM-ICPC, Topcoder Open, Facebook Hacker Cup and Google Code Jam. I got a second place in Google Code Jam 2018. Watch me if you want to practice Competitive Programming, algorithms or you want to learn for a coding interview. I share my thought process, explain everything, and mention similar problems that I know or techniques/algorithms that could be used too. Learn from me and grow your rating on Codeforces!

[nullnull]

dude, keep doing this, this is original content.

[abhijeetkrishnan]

Thank you for this! It helped me a lot with solving some problems in a recent Codechef contest.

[Nampjg]

One of th best tutorials for programmers .... Thanks Errichto

[indiansoftwareengineer]

I am also using Linux, Ubuntu 18.04.
loved your channel and getting lot of motivation from your channel.

[prateeksinghal]

With this video, I not only learn about up solving but also Linux commands :P

[harivilas]

Most Helpful Video of Youtube Ever Seen

[shameekagarwal]

very useful for codechef were testcases arent shown which becomes difficult while upsolving

[hutofrock]

Nice video, thanks!

How would you test a solution with multiple correct answers?
For example, let's consider the following problem: "Given a number N (N > 2), print a positive number less than N". Obviously there are multiple correct answers, but the brute force solution might return something different than the other solution. In this case just diff-ing the output is not sufficient. :)

Maybe in such cases an additional checker program should be provided. However, it might sometimes seem that writing an efficient solution + brute force solution + checker could be very time consuming.

[shubhamk]

Thanks, I wanted to know it and, its pretty awesome the way it works.

[Xenox_dev]

Great video. I like this approach to testing. The script is simple so you can easily write it during a contest. I prefer using an extension for VS Code to test my solution on my laptop. I guess it's up to you what you choose.

In 0:29, there is a small mistake in eng subs. Instead of "you CANT submit a solution" should be "you CAN submit a solution". That would be stupid if you couldn't submit a solution on contest :)

[Pauljanson]

How to debug the problems ? after finding a breaking test case in case of a backtracking solution which is harder to debug using breakpoints?

[getintodevices]

Awesome! Are you still considering DP contest from AtCoder in some next stream?

[nafiurrahmankhadem]

Please make a video on testing interactive problems' solutions efficiently.

[satyajeetkumar]

Sir how to generate random test cases if the given input is a tree

[piotrbublik]

How to test on large input files? For example 20000 KB size of input file

[Golovanov]

Outside a script I think it's more convenient to use "git diff", not "diff"

[vishnuvs]

Does this mean that we need to have a brute force solution for the question in order to check it? What happens when the solutions are not easy and we can't find the bute force solution?

[lovleshbhatt]

How to do the same things in WIndows??

[adityasher]

Thank you very much, I will watch it.

[theeasypeasysquad]

i was trying this. The only change I made was not to generate unique numbers. So i removed do..while loop. Problem is for a given seed
value, I am always generating same sequence. The code is :

#include<bits/stdc++.h>
using namespace std;


int rand(int a, int b)
{
return (a + rand() % (b-a+1));
}

int main(int argc, char* argv[])
{
//srand(time(0));
srand(atoi(argv[1]));
int n=rand(2, 10);
printf("%d\n", n);
for(int i=1;i<=n;i++)
{
int x;
x=rand(1, 10);
printf("%d ", x);
}
puts("");
}

and for seed 1, that is, ./gen 1 this is the output i always get
3
7 8 6
i want the numbers generated to be repetitive and not unique. Any solution to that ?

edit: Even running the same code as in video is giving me same sequence of integers every time for a given seed

Edit 2: i just learnt that rand() generates a pseudo random sequence. So thats the reason the values are fixed for a particular sequence.

So i just change my question. Is there any way to fix this issue. I have used srand(time(NULL)) but its time interval is 1 second. So the seed is fixed for one second. In one second if i have to generate multiple sequence there seed is same so the sequence is same. Can we generate a truly random sequence in c++ ?