LC-2001 Medium LeetCode

2001. Number of Pairs of Interchangeable Rectangles

Array Hash Table Math Counting Number Theory

Read the full problem statement on LeetCode.

Difficulty: medium Acceptance: 51% Topics: Array, Hash Table, Math, Counting, Number Theory

Reading material

Arrays & Hashing 12 min Math & Geometry 12 min

Reference solution (spoiler · python)

# Time:  O(n)
# Space: O(n)

import collections
import fractions


class Solution(object):
    def interchangeableRectangles(self, rectangles):
        """
        :type rectangles: List[List[int]]
        :rtype: int
        """
        count = collections.defaultdict(int)
        for w, h in rectangles:
            g = fractions.gcd(w, h)  # Time: O(logx) ~= O(1)
            count[(w//g, h//g)] += 1
        return sum(c*(c-1)//2 for c in count.itervalues())

Solution from kamyu104/LeetCode-Solutions · MIT