leetcode 4. Median of Two Sorted Arrays

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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)).

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

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class Solution(object):
    def findMedianSortedArrays(self, nums1, nums2):
        """
        :type nums1: List[int]
        :type nums2: List[int]
        :rtype: float
        """
        m,n = len(nums1),len(nums2)
        if m > n:
            nums1,m,nums2,n = nums2,n,nums1,m
        
        begin ,end = 0,m
        
        while begin <= end:
            i = (begin+end)/2
            j = (m+n+1)/2 - i
            if i > 0 and nums1[i-1] > nums2[j] :
                #i is too large
                end = i - 1
            elif i < m and nums1[i] < nums2[j-1] :
                #i is too small
                begin = i + 1 
            else:#i is ok
                if i == 0:max_left = nums2[j-1]
                elif j == 0:max_left = nums1[i-1]
                else:
                    max_left = max(nums1[i-1],nums2[j-1])
                
                if (m + n)%2 == 1:
                    return max_left
                
                if i == m:min_right = nums2[j]
                elif j == n:min_right = nums1[i]
                else:
                    min_right = min(nums2[j],nums1[i])
                return (min_right+max_left)/2.0