[LeetCode] 051: Median of Two Sorted Arrays

[Problem]
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)).

[Solution]

class Solution{
public:
// find the kth element of two sorted arrays
double findKth(int *A, int m, int *B, int n, int k){
// invalid k
if(k <= 0 || k > m + n)return 0;

// because i=min(k/2, m), j=k-i, so i <= j, we should make sure m <= n
if(m > n)return findKth(B, n, A, m, k);

// either A or B is empty
if(m == 0)return B[k-1];
if(n == 0)return A[k-1];

// the first of the two sorted arrays
if(k == 1)return min(A[0], B[0]);

// binary search
int i = min(k/2, m), j = k - i;
if(A[i-1] < B[j-1]){
return findKth(A+i, m-i, B, n, k-i);
}
else if(A[i-1] > B[j-1]){
return findKth(A, m, B+j, n-j, k-j);
}
else{
return A[i-1];
}
}
// find the median of two sorted arrays
double findMedianSortedArrays(int A[], int m, int B[], int n){
// Start typing your C/C++ solution below
// DO NOT write int main() function
if((m+n) % 2 == 0){
return (findKth(A, m, B, n, (m+n)/2) + findKth(A, m, B, n, (m+n)/2+1)) / 2;
}
else{
return findKth(A, m, B, n, (m+n)/2+1);
}
}
};

说明：版权所有，转载请注明出处。Coder007的博客