Leetcode 04 Median of Two Sorted Arrays

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)).

class Solution
{
private:
typedef vector<int>::const_iterator ITE;
public:
double findkth(ITE l1, ITE r1, ITE l2, ITE r2, int k)
{
if (r1 - l1 > r2 - l2) return findkth(l2, r2, l1, r1, k);
if (l1==r1) return *(l2+k-1);
if (k == 1) return min(*l1, *l2);
int pa = min(int(r1 - l1), k / 2), pb = k - pa;
ITE lpa = l1 + pa - 1, lpb = l2 + pb - 1;
if (*lpa < *lpb) return findkth(l1 + pa, r1, l2, r2, pb);
else
if (*lpa > *lpb)
{
return findkth(l1, r1, l2 + pb, r2, pa);
}
else
{
return *lpa;
}
}
double findMedianSortedArrays(vector<int>& nums1, vector<int>& nums2)
{
int m = nums1.size(), n = nums2.size(), total = m + n;
ITE l1 = nums1.begin(), r1 = nums1.end();
ITE l2 = nums2.begin(), r2 = nums2.end();
if (total % 2) return findkth(l1, r1, l2, r2, total / 2 + 1);
else
{
return (findkth(l1, r1, l2, r2, total / 2) + findkth(l1, r1, l2, r2, total / 2 + 1))/2;
}
}
};