735. Asteroid Collision
Asteroid Collision (LeetCode 735) is a Medium Data Structures and Algorithms interview problem you can solve, run and submit on Thita.ai. It belongs to the Stack Patterns pattern, in the Simulation / Backtracking Helper subpattern.
How to solve Asteroid Collision
Asteroid Collision is a Stack for Simulation and Backtracking problem, part of Stack Patterns. Use stack for simulation problems like simplify path, decode string, and asteroid collision.
Work towards the solution in these steps:
- Say a row of asteroids is stable. What happens when a new asteroid is added on the right?
The reference solution runs in O(n) time and O(n) space.
The Asteroid Collision solution and editorial walks through the full approach with reference code.
Problem statement
We are given an array asteroids of integers representing asteroids in a row. The indices of the asteriod in the array represent their relative position in space.
For each asteroid, the absolute value represents its size, and the sign represents its direction (positive meaning right, negative meaning left). Each asteroid moves at the same speed.
Find out the state of the asteroids after all collisions. If two asteroids meet, the smaller one will explode. If both are the same size, both will explode. Two asteroids moving in the same direction will never meet.
Example 1:
Input: asteroids = [5,10,-5] Output: [5,10] Explanation: The 10 and -5 collide resulting in 10. The 5 and 10 never collide.
Example 2:
Input: asteroids = [8,-8] Output: [] Explanation: The 8 and -8 collide exploding each other.
Example 3:
Input: asteroids = [10,2,-5] Output: [10] Explanation: The 2 and -5 collide resulting in -5. The 10 and -5 collide resulting in 10.
Constraints:
- 2 <= asteroids.length <= 10^4
- -1000 <= asteroids[i] <= 1000
- asteroids[i] != 0
Topics and companies
Topics: Array, Stack, Simulation.
Reported in interviews at Amazon, Lyft, ByteDance, Oracle.
How to practise Asteroid Collision on Thita.ai
Starter code is provided in C, C#, C++, Go, Java, JavaScript and Python. Your solution runs against 5 test cases for this problem, with the AI coach available for a hint when you are stuck rather than a finished answer. The reference solution runs in O(n) time and O(n) space.
Open Asteroid Collision in the code editor, or read the Asteroid Collision editorial for a worked solution with its approach and complexity analysis.
Where Asteroid Collision sits in the DSA pattern sheet
Problems related to Asteroid Collision
Other problems that use the same Simulation / Backtracking Helper and Stack Patterns techniques:
- Baseball Game — Easy, same subpattern
- Decode String — Medium, same subpattern
- Reconstruct Itinerary — Hard, same subpattern
- Simplify Path — Medium, same subpattern
- Basic Calculator — Hard, same pattern
- Basic Calculator II — Medium, same pattern
Asteroid Collision FAQ
What is the LeetCode number of Asteroid Collision?
Asteroid Collision is LeetCode problem 735, rated Medium.
What pattern is used to solve Asteroid Collision?
Asteroid Collision is a Stack for Simulation and Backtracking problem. It belongs to the Stack Patterns pattern, in the Simulation / Backtracking Helper subpattern.
What is the time complexity of Asteroid Collision?
The reference solution runs in O(n) time and O(n) space.
Which companies ask Asteroid Collision?
Asteroid Collision has been reported in interviews at Amazon, Lyft, ByteDance, Oracle.