Time Limit Exceeded in Competitive Programming | TLE | Time Complexity in Coding | Coding Winds | We Care about the future of future

Time Limit Exceeded

"Why is the time limit of code exceeding?" This is a question which every competitive programmer has, it doesn’t matter whichever platform (Hackerrank,  Hackerearth, CodeChef, Codeleet or any other) they are using , some or the other day they face this “Time limit exceeded” problem. To clear your doubts regarding this, read this article, we assure you, you will have a solution to the “Time limit exceeded” pop-up next time.

First of all, we need to understand something about compiling of code in competitive programming

In competitive programming, your code is tested by a code-checker automatically, not by a human being, and you have to write your code accordingly.

For each problem, there will be one or more input files, each according to the specifications mentioned in the problem statement, and corresponding correct output files. Your program is run on each of the input files by redirecting the standard input stream to an input file, and the standard output stream to another file. The output generated by your program must match the correct output exactly in order to be judged correct.

Note that your program must read from stdin and print to stdout. This means using scanf/printf in C, cin/cout in C++ and similarly in other languages.

To understand more about “Time Limit Exceeded(TLE)”, understanding how the online checker works will help. The online judge allocates resources like memory and CPU for evaluating every submission.

However, to ensure that your submission does not keep running for an infinite time, the online judge has to stop your submission from running after a particular time period. This time period is actually decided by the problem setter and is given as one of the inputs to the online judge. Once the submission program runs for time period the judge system issues a system kill command to the program execution and assigns TLE result to the submission.

The most common reason that you would get a TLE is because your program is too slow. If a problem tells you that N <= 100000, and your program has nested loops each which go up to N, your program will never be fast enough. Read the bounds in the input section carefully before writing your program, and try to figure out which inputs will cause your program to run the slowest.

The second most common cause of TLE is that your method of reading input and writing output is too slow. 

In Java, do not use a Scanner; use a BufferReader instead. In C++, do not use cin/cout - use scanf and printf instead.

In Python, you could try speeding up your solutions by adding the following two lines to the start of your file:

import psyco 

psyco.full()

To see if your method of reading input is fast enough, try solving the Enormous Input Test problem. If you get time limit exceeded, try another method of reading input.

Finally, you may have tested your code on all sorts of large inputs and are sure your code will run inside the time limit. However, online judge may be slower than your computer. It is common for a program to take 2-3 times longer on online platform as it does on your computer. The time limits are all attainable (tested by our problem tester), so you will just need to come up with a way of making your algorithm.

 

Hope all your doubts regarding this are clear now.

If you still have any doubt on this topic then do come to us via email "sophomoretechs@gmail.com" or via instagram "@coding.winds".

We also have an article on space complexity and time complexity , do give them a read.