4. Median of Two Sorted Arrays

class Solution:
  def findMedianSortedArrays(self, nums1, nums2):
    """
    :type nums1: List[int]
    :type nums2: List[int]
    :rtype: float
    """

    # print(nums1)
    # print(nums2)
    l1 = len(nums1)
    l2 = len(nums2)

    if l1 < l2:
        l1, l2 = l2, l1
        nums1, nums2 = nums2, nums1

    m1 = l1 // 2
    m2 = l2 // 2

    if l2 <= 4:
        for i in range(l2):
            self.insert(nums1, nums2[i])
        #print(nums1)
        if (l1 + l2) % 2 == 1:
            return float(nums1[(l1 + l2) // 2])
        else:
            #print(1)
            return (nums1[(l1 + l2) // 2 - 1] + nums1[(l1 + l2 ) // 2]) / 2
        #print(1)

    if nums1[m1] > nums2[m2]:
        return(self.findMedianSortedArrays(nums1[ : l1 - m2 + 1], nums2[m2 - 1: ]))
    else:
        return(self.findMedianSortedArrays(nums1[l2 - m2 - 2:],nums2[ : m2 + 2] ))

def insert(self, nums, a):
    """
    :type nums1: List[int]
    :type a: int
    :rtype: None
    """
    l = 0
    r = len(nums) - 1
    #print(nums, l, r, a)
    while l < r - 1:
        m = (l + r) // 2
        if nums[m] < a:
            l = m + 1
        elif nums[m] > a:
            r = m - 1
        else:
            #print(nums, l, r, a)
            nums.insert(m, a)
            return
    #print(nums, l, r, a)
    if l == r - 1:
        if a > nums[r]:
            nums.insert(r + 1, a)
        elif a > nums[l]:
            nums.insert(l + 1, a)
        else:
            nums.insert(l, a)
    else:
        if a > nums[l]:
            nums.insert(l + 1, a)
        else:
            nums.insert(l, a)

以上是我自己的解法，搜了下有更好的解法。于是我对着解法又敲了遍代码。

refererence: to https://leetcode.com/problems/median-of-two-sorted-arrays/solution/

class Solution:
    def findMedianSortedArrays(self, nums1, nums2):
        """
        :type nums1: List[int]
        :type nums2: List[int]
        :rtype: float
        """
        m = len(nums1)
        n = len(nums2)

        if m > n:
            m, n = n, m
            A, B = nums2, nums1
        else:
            A, B = nums1, nums2

        l = 0
        r = m

        while l <= r:
            i = (l + r) // 2
            j = (m + n + 1) // 2 - i
            # print(l, r)
            # print(i, j)
            if (i < m) and (A[i] < B[j - 1]):
                l = i + 1
            elif (i > 0) and (A[i - 1] > B[j]):
                r = i - 1
            else:
                if (m + n) % 2 == 0:
                    ans1 = -999999;
                    if i > 0:
                        ans1 = max(ans1, A[i - 1])
                    if j > 0:
                        ans1 = max(ans1, B[j - 1])
                    ans2 = 999999;
                    if i < m:
                        ans2 = min(ans2, A[i])
                    if j < n:
                        ans2 = min(ans2, B[j])
                    #print (ans1, ans2)
                    return (ans1 + ans2) / 2
                else:
                    ans = -999999;
                    if i > 0:
                        ans = max(ans, A[i - 1])
                    if j > 0:
                        ans = max(ans, B[j - 1])
                    return ans