leetcode 4. Median of Two Sorted Arrays

class Solution {
public:
    double findMedianSortedArrays(vector<int>& nums1, vector<int>& nums2) {
        int length1 = nums1.size();
        int length2 = nums2.size();
        int len = length1 + length2;
        int mid = len/2;
        if(len % 2 == 0)
            return (findKthNumber(nums1,nums2,0,0,mid) + findKthNumber(nums1,nums2,0,0,mid+1))/2.0;
        else
            return findKthNumber(nums1,nums2,0,0,mid+1);
    }
        
    int findKthNumber(vector<int> nums1,vector<int> nums2,int start1,int start2,int k){
        int length1 = nums1.size();
        int length2 = nums2.size();
        if(start1 >= length1)
            return nums2[start2+k-1];
        if(start2 >= length2)
            return nums1[start1+k-1];
        if(k == 1)
            return min(nums1[start1],nums2[start2]);
        int mid = k/2 - 1;
        int num1 = start1 + mid >= length1 ? 0x7FFFFFFF : nums1[start1 + mid];
        int num2 = start2 + mid >= length2 ? 0x7FFFFFFF : nums2[start2 + mid];
        if(num1 > num2)
            return findKthNumber(nums1,nums2,start1,start2 + mid + 1,k-k/2);
        else
            return findKthNumber(nums1,nums2,start1 + mid + 1,start2,k-k/2);        
    }
    
};