Median of Two Sorted Arrays

 1 class Solution {
 2 public:
 3     double findMedianSortedArrays( int A[], int m, int B[], int n ) {
 4         int a1 = FindKthNum( (m+n-1)/2, A, m, B, n );
 5         int a2 = FindKthNum( (m+n)/2, A, m, B, n );
 6         return ( a1 + a2 ) / 2.0;
 7     }
 8 private:
 9     int FindKthNum( int k, const int* A, int m, const int* B, int n ) {
10         if( m == 0 ) { return B[k]; }
11         if( n == 0 ) { return A[k]; }
12         if( k == 0 ) { return A[0] < B[0] ? A[0] : B[0]; }
13         int k1 = -1, k2 = -1;
14         if( m < n ) {
15             k1 = min( k/2, m-1 ), k2 = k - k1 - 1;
16         } else {
17             k2 = min( k/2, n-1 ), k1 = k - k2 - 1;
18         }
19         if( A[k1] < B[k2] ) {
20             return FindKthNum( k2, &A[k1+1], m-k1-1, &B[0], k2+1 );
21         } else if( A[k1] > B[k2] ) {
22             return FindKthNum( k1, &A[0], k1+1, &B[k2+1], n-k2-1 );
23         }
24         return B[k2];
25     }
26 };