“Programming isn’t about what you know; it’s about what you can figure out.”
~Chris Pine

Day 8 of the May LeetCoding Challenge by Leetcode

Learning something new is always an advantage! There is no wrong method when it comes to learning, find a way that suits you the best. Learn by reading a book, attend online seminars or signup for an online course but make sure to challenge yourself.

If not now, then when? The lockdown has given you an opportunity to better yourself, do something positive for your personal growth and development.

Problem definition: Check If It Is a Straight Line

You are given an array coordinates, coordinates[i] = [x, y], where [x, y] represents the coordinate of a point. Check if these points make a straight line in the XY plane.

Constraints:

• 2 <= coordinates.length <= 1000
• coordinates[i].length == 2
• -10^4 <= coordinates[i][0], coordinates[i][1] <= 10^4
• coordinates contains no duplicate point.

Sample Testcase

Testcase 1

Input: coordinates = [[1,2],[2,3],[3,4],[4,5],[5,6],[6,7]]
Output: true

Testcase 2

Input: coordinates = [[1,1],[2,2],[3,4],[4,5],[5,6],[7,7]]
Output: false

Hints

• If there’re only 2 points, return true.
• Check if all other points lie on the line defined by the first 2 points.
• Use cross product to check collinearity.

I highly encourage you to attempt this problem on your own before looking at my solution.

Approach

Obtain the equation of the line that passes through the first two points. ( if the input contains only two points, return True ) Starting the iteration from the third point, check if the point lies on the equation computed previously. As soon as a point does not satisfy the equation, return False.

Solution

class Solution:
    def checkStraightLine(self, coordinates: List[List[int]]) -> bool:
        if(len(coordinates)==2):
            return True
        else:
            a = coordinates[1][1] - coordinates[0][1] 
            b = coordinates[0][0] - coordinates[1][0]  
            c = a*(coordinates[0][0]) + b*(coordinates[0][1]) 
            for i in range(2,len(coordinates)):
                    if((a*coordinates[i][0] + b*coordinates[i][1])!=c):
                        return False   
            return True

Submission Details

Total test cases passed: 66 / 66
Runtime: 56 ms
Memory Usage: 13.9 MB

Note: This submission was better than 92.73% of Python3 solutions in terms of runtime. Try to come up with a solution that is more optimal! 🌚

I would really recommend you to explore this side of the Computer Science and tune in to the journey of competitive programming to write better, cleaner, efficient and optimal code! 😀

If you have a better approach to this problem, or for any other queries feel free to reach out to me! 😇