4.Median of Two Sorted Arrays

public class Solution {
    public double findMedianSortedArrays(int[] nums1, int[] nums2) {
        int len = nums1.length + nums2.length;
        if (len % 2 == 1) {
            return findKth(nums1, 0, nums2, 0, len / 2 + 1);
        }
        return (
            findKth(nums1, 0, nums2, 0, len / 2) + findKth(nums1, 0, nums2, 0, len / 2 + 1)
        ) / 2.0;
    }

    // find kth number of two sorted array
    public static int findKth(int[] A, int A_start,
                              int[] B, int B_start,
                              int k){		
		if (A_start >= A.length) {
			return B[B_start + k - 1];
		}
		if (B_start >= B.length) {
			return A[A_start + k - 1];
		}

		if (k == 1) {
			return Math.min(A[A_start], B[B_start]);
		}
		
		int A_key = A_start + k / 2 - 1 < A.length
		            ? A[A_start + k / 2 - 1]
		            : Integer.MAX_VALUE;
		int B_key = B_start + k / 2 - 1 < B.length
		            ? B[B_start + k / 2 - 1]
		            : Integer.MAX_VALUE; 
		
		if (A_key < B_key) {
			return findKth(A, A_start + k / 2, B, B_start, k - k / 2);
		} else {
			return findKth(A, A_start, B, B_start + k / 2, k - k / 2);
		}
	}
}