Understand what the interviewer is asking for by using test cases and questions about the problem.
- Established a set (2-3) of test cases to verify their own solution later.
- Established a set (1-2) of edge cases to verify their solution handles complexities.
- Have fully understood the problem and have no clarifying questions.
- Have you verified any Time/Space Constraints for this problem?
Be sure that you clarify the input and output parameters of the problem:
N
being the number, O(logN)
time and O(1)
space.Run through a set of example cases:
HAPPY CASE
Input: n = 27
Output: true
Explanation: 27 = 3^3
Input: n = -1
Output: false
Explanation: There is no x where 3x = (-1).
EDGE CASE
Input: n = 0
Output: false
Explanation: There is no x where 3^x = 0.
Input: n = 1
Output: true
Explanation: 2^0 = 1
Match what this problem looks like to known categories of problems, e.g. Linked List or Dynamic Programming, and strategies or patterns in those categories.
For problems outside of the main catagories, we want to consider the input and output:
We are working with a number and checking if it is a power of three. We know for sure any number is a power of three if it can be divided by three until it becomes 1, along the way down it must also be divisible by three.
Plan the solution with appropriate visualizations and pseudocode.
General Idea: We will recursively divide the number by 3 until it either reaches 1 and return true or it is no longer a whole number when divided by 3 and return false. We also need to consider the edge case 0, which is false.
1. Break into base case where n = 1 return True
2. Break into base case where n = 0 or n is no longer a whole number when divided by 3 return False
3. Return the recursive function n/3
⚠️ Common Mistakes
Implement the code to solve the algorithm.
class Solution:
def isPowerOfThree(self, n: int) -> bool:
# Break into base case where n = 1 return True
if n == 1:
return True
# Break into base case where n = 0 or n is no longer a whole number when divided by 3 return False
if n == 0 or n % 3 != 0:
return False
# Return the recursive function n/3
return self.isPowerOfThree(n/3)
class Solution {
public boolean isPowerOfThree(int n) {
// Break into base case where n = 1 return True
if(n == 1) return true;
// Break into base case where n = 0 or n is no longer a whole number when divided by 3 return False
if(n == 0 || n % 3 != 0) return false;
// Return the recursive function n/3
return isPowerOfThree(n/3);
}
}
Review the code by running specific example(s) and recording values (watchlist) of your code's variables along the way.
Evaluate the performance of your algorithm and state any strong/weak or future potential work.
Assume N represents the number given