Circular Array Loop
Explore how to detect cycles in circular arrays using fast and slow pointers. Understand the conditions for a valid loop and implement solutions to identify repeating sequences within array indices.
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Statement
There is a circular list of non-zero integers called nums. Each number in the list tells you how many steps to move forward or backward from your current position:
If
nums[i]is positive, movenums[i]steps forward.If
nums[i]is negative, movenums[i]steps backward.
As the list is circular:
Moving forward from the last element takes you back to the first element.
Moving backward from the first element takes you to the last element.
A cycle in this list means:
You keep moving according to the numbers, and you end up repeating a sequence of indexes.
All numbers in the cycle have the same sign (either all positive or all negative).
The cycle length is greater than 1 (it involves at least two indexes).
Return true if such a cycle exists in the list or false otherwise.
Constraints:
-
nums.length -
nums[i] nums[i]
Examples
Understand the problem
Let’s take a moment to make sure you’ve correctly understood the problem. The quiz below helps you check if you’re solving the correct problem:
Circular Array Loop
(True or False) The following array contains a cycle.
[3, -3, 2, -2]
True
False
Figure it out!
We have a game for you to play. Rearrange the logical building blocks to develop a clearer understanding of how to solve this problem.
Try it yourself
Implement your solution in the following coding playground.
function circularArrayLoop(nums){// Replace this placeholder return statement with your codereturn false;}export {circularArrayLoop}