Binary search. Call 2 times getkth and k is about half of (m + n). Every time call getkth can reduce the scale k to its half. So the time complexity is log(m + n).

```
class Solution {
public:
int getkth(int s[], int m, int l[], int n, int k){
// let m <= n
if (m > n)
return getkth(l, n, s, m, k);
if (m == 0)
return l[k - 1];
if (k == 1)
return min(s[0], l[0]);
int i = min(m, k / 2), j = min(n, k / 2);
if (s[i - 1] > l[j - 1])
return getkth(s, m, l + j, n - j, k - j);
else
return getkth(s + i, m - i, l, n, k - i);
return 0;
}
double findMedianSortedArrays(int A[], int m, int B[], int n) {
int l = (m + n + 1) >> 1;
int r = (m + n + 2) >> 1;
return (getkth(A, m ,B, n, l) + getkth(A, m, B, n, r)) / 2.0;
}
};
```