1232 Check If It Is a Straight Line - Easy

Problem:

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.

Example 1:

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

Example 2:

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

Constraints:

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

Problem Analysis:

• Base case: if there are only 2 points, it is guaranteed true

• Find the slope of the first 2 points

• Return true if all the slope between points are the same

• Time Complexity: O(n)

• Space Complexity: O(1)

Solutions:

class Solution:
    def checkStraightLine(self, coordinates: List[List[int]]) -> bool:
        if len(coordinates) <= 2:
            return True
        
        # calculate slope
        x0, y0 = coordinates[0]
        x1, y1 = coordinates[1]
        initial_slope = (y1 - y0) / (x1 - x0) if (x1 - x0) != 0 else float('inf')

        # check slope
        for i in range(2, len(coordinates)):
            xi, yi = coordinates[i]
            current_slope = (yi - y0) / (xi - x0) if (xi - x0) != 0 else float('inf')

            # if slope dont match
            if current_slope != initial_slope:
                return False        

        return True```

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