How hard is LeetCode 469. Convex Polygon?

LeetCode 469. Convex Polygon is rated Medium on LeetCode.

What topics does LeetCode 469. Convex Polygon cover?

LeetCode 469. Convex Polygon is tagged Geometry, Array and Math on LeetCode.

Is LeetCode 469. Convex Polygon a premium problem?

Yes. LeetCode 469. Convex Polygon is a LeetCode Premium problem, so the full statement and test cases require a paid LeetCode subscription.

Convex Polygon — LeetCode 469 Python Solution

MediumLeetCode PremiumGeometryArrayMath

Problem: #469
Pattern: Math and Number Theory
Reading time: 3 min
Source: leetcode.com

The problem

You are given an array of points on the X-Y plane points where points[i] = [xi, yi]. The points form a polygon when joined sequentially.

Example

Input: points = [[0,0],[0,5],[5,5],[5,0]]
Output: true

Python solution

Python

class Solution:
    def isConvex(self, points: List[List[int]]) -> bool:
        n = len(points)
        pre = cur = 0
        for i in range(n):
            x1 = points[(i + 1) % n][0] - points[i][0]
            y1 = points[(i + 1) % n][1] - points[i][1]
            x2 = points[(i + 2) % n][0] - points[i][0]
            y2 = points[(i + 2) % n][1] - points[i][1]
            cur = x1 * y2 - x2 * y1
            if cur != 0:
                if cur * pre < 0:
                    return False
                pre = cur
        return True

Complexity

Measure	Complexity
Time	O(n) or O(1)
Space	O(1) auxiliary

Pattern: Math and Number Theory

Find the closed form, the invariant, or the modular identity — and skip the loop entirely. LeetCode 469. Convex Polygon is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Math and Geometry.

The math and number theory guide has the Python template for the pattern and the 485 LeetCode problems that use it.

Frequently asked questions

How hard is LeetCode 469. Convex Polygon?: LeetCode 469. Convex Polygon is rated Medium on LeetCode.
What topics does LeetCode 469. Convex Polygon cover?: LeetCode 469. Convex Polygon is tagged Geometry, Array and Math on LeetCode.
Is LeetCode 469. Convex Polygon a premium problem?: Yes. LeetCode 469. Convex Polygon is a LeetCode Premium problem, so the full statement and test cases require a paid LeetCode subscription.