LeetCode 4. Median of Two Sorted Arrays

        public double FindMedianSortedArrays(int[] nums1, int[] nums2)
        {
            int m = nums1.Length;
            int n = nums2.Length;
            int total = m + n;
            if (total % 2 == 1)
                return findKth(nums1, m, nums2, n, total / 2 + 1);
            else
                return (findKth(nums1, m, nums2, n, total / 2)
                        + findKth(nums1, m, nums2, n, total / 2 + 1)) / 2;
        }

        //比较a[k/2] 和b[k/2], 将较小的那个数组的前k/2部分删除；循环这个过程
        double findKth(int[] a, int m, int[] b, int n, int k)
        {
            //always assume that m is equal or smaller than n  
            if (m > n)
                return findKth(b, n, a, m, k);
            if (m == 0)
                return b[k - 1];
            if (k == 1)
                return Math.Min(a[0], b[0]);
            //divide k into two parts  
            int pa = Math.Min(k / 2, m), pb = k - pa;
            if (a[pa - 1] < b[pb - 1])
            {
                int[] newA = a.Skip(pa).ToArray();
                return findKth(newA, m - pa, b, n, k - pa);
            }
            else if (a[pa - 1] > b[pb - 1])
            {
                int[] newB = b.Skip(pb).ToArray();
                return findKth(a, m, newB, n - pb, k - pb);
            }
            else
                return a[pa - 1];
        }