use of constraints

general
1

i do not understand the use of constraints in my question…please help!

2

Constraints are given so that you can check if your algorithm will run in the given time limit or not (cause Time Limit Exceeded error) .

For Example, if Constraints say n<=10^4,

Then O(n) and O(n^2) algorithms will work while O(n^3) algorithms will cause time limit exceeded error.