class Solution {
public:
    double findMedianSortedArrays(vector<int>& nums1, vector<int>& nums2) {
        int total = nums1.size() + nums2.size();
        if (total % 2 == 1) {
            return findKth(nums1, 0, nums2, 0, total / 2 + 1);
        } else {
            return (findKth(nums1, 0, nums2, 0, total / 2) + findKth(nums1, 0, nums2, 0, total / 2 + 1)) / 2;
        }
    }
    double findKth(vector<int> &nums1, int i, vector<int> &nums2, int j, int k) {
        if (nums1.size() - i > nums2.size() - j) return findKth(nums2, j, nums1, i, k);
        if (nums1.size() == i) return nums2[j + k - 1];
        if (k == 1) return min(nums1[i], nums2[j]);
        int pa = min(i + k / 2, int(nums1.size())), pb = j + k - pa + i;
        if (nums1[pa - 1] < nums2[pb - 1]) 
            return findKth(nums1, pa, nums2, j, k - pa + i);
        else if (nums1[pa - 1] > nums2[pb - 1]) 
            return findKth(nums1, i, nums2, pb, k - pb + j);
        else 
            return nums1[pa - 1];
    }
};

leetcode 4 Median of Two Sorted Arrays