Median of Two Sorted Arrays [hard]

There are two sorted arrays A and B 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)).

思路：1.可以转换为寻找第k小的数。if m+n is odd, find (m+n)/2 th is ok; if m+n is even ,find (m+n)/2 th and (m+n)/2+1 th, then get the average.

时间复杂度，在m+n的长度下每次剔除k/2, like  binary search, 所以为O(lg(m+n));

2.另一种方法的时间复杂度是O(lgmin(n,m)) 还没看懂，待我我再看~~~~

class Solution {
public:
    double findMedianSortedArrays(int A[], int m, int B[], int n) {
        if(m==0 && n==0) return 0;
        int total = m+n;
        if(total%2==1) return findKth(A,0,m-1,B,0,n-1,total/2 + 1);
        else return (findKth(A,0,m-1,B,0,n-1,total/2)+findKth(A,0,m-1,B,0,n-1,total/2+1))/2;
    }

    double findKth(int A[], int al, int ah, int B[], int bl, int bh, int k){

        int m = ah-al+1;
        int n = bh-bl+1;
        if(m>n) return findKth(B,bl,bh,A,al,ah,k);
        if(m==0) return B[k-1];
        else if(k==1) return min(A[al],B[bl]);

        int pa = min(k/2,m);
        int pb = k-pa;
        if(A[al+pa-1]<B[bl+pb-1]) return findKth(A,al+pa,ah,B,bl,bh,k-pa);
        else if(A[al+pa-1]>B[bl+pb-1]) return findKth(A,al,ah,B,bl+pb,bh,k-pb);
        else return A[al+pa-1];
    }
};

上面代码写的很繁琐，需要改进。尤其是计算 al 和 ah时特别容易出错。 有啥好方法捏？？？？