88. merge sorted array

class (object):
    def merge(self, nums1, m, nums2, n):
        """
        :type nums1: List[int]
        :type m: int
        :type nums2: List[int]
        :type n: int
        :rtype: void Do not return anything, modify nums1 in-place instead.
        """
        if n == 0:
            return
        p1, p2 = m - 1, n - 1  
        for i in range(m + n - 1, -1, -1):
            if p1 < 0:
                nums1[i] = nums2[p2]
                p2 -= 1
            elif p2 < 0:
                nums1[i] = nums1[p1]
                p1 -= 1
            elif nums1[p1] > nums2[p2]:
                nums1[i] = nums1[p1]
                p1 -= 1
            elif nums1[p1] <= nums2[p2]:
                nums1[i] = nums2[p2]
                p2 -= 1