Leetcode4答案与解析 - Median of Two Sorted Arrays(python)

原题

Leetcode原题传送门

There are two sorted arrays nums1 and nums2 of size m and n respectively.

Find the median of the two sorted arrays. The overall run time complexity should be O(log (m+n)).

You may assume nums1 and nums2 cannot be both empty.

Example 1:

nums1 = [1, 3]
nums2 = [2]

The median is 2.0

Example 2:

nums1 = [1, 2]
nums2 = [3, 4]

The median is (2 + 3)/2 = 2.5

解析

TBD(该坑挖于2018.10.14)

运行速度

运行速度： 96 ms | 超过93.73%的cpp程序

Note: 这不是我的实现，参考了Link

答案

# It is not my solution but:
# https://leetcode.com/problems/median-of-two-sorted-arrays/discuss/2567/Python-O(log(min(mn))-solution
# my own solution is too trivial to realize

class Solution:
    def findMedianSortedArrays(self, A, B):
        l = len(A) + len(B)
        return self.findKth(A, B, l // 2) if l % 2 == 1 else (self.findKth(A, B, l // 2 - 1) + self.findKth(A, B, l // 2)) / 2.0

    def findKth(self, A, B, k):
        if len(A) > len(B):
            A, B = B, A
        if not A:
            return B[k]
        assert k <= len(A) + len(B) - 1
        if k == len(A) + len(B) - 1:
            return max(A[-1], B[-1])
        i = len(A) // 2
        j = k - i
        if A[i] > B[j]:
            return self.findKth(A[:i], B[j:], i)
        else:
            return self.findKth(A[i:], B[:j], j)


if __name__ == "__main__":
    sol = Solution()
    print(sol.findMedianSortedArrays([2, 4, 7], [1, 6]))