double findMedianSortedArrays(int A[], int m, int B[], int n)
{
if((m+n)%2==1)
{
return (double)findMedianIndex(A,m,B,n,(m+n+1)/2);
}
return ((double)findMedianIndex(A,m,B,n,(m+n)/2)+(double)findMedianIndex(A,m,B,n,(m+n)/2+1))/2;
}
/*Computes the median of each group of 5 elements and stores
it as the first element of the group (left). Recursively does this
till there is only one group and hence only one Median */
mwSize findMedianOfMedians(mwSize left, mwSize right)
{
mwSize i, shift, step, tmp;
mwSize endIndex, medianIndex;
if (left==right) return left;
shift = 1;
while (shift <= (right-left))
{
step=shift*5;
for (i=left; i<=right; i+=step)
{
if ((endIndex=i+step-1)>=right)
endIndex=right;
medianIndex = findMedianIndex(i, endIndex, shift);
/* Swap pos[i] with pos[medianIndex] */
tmp = pos[i];
pos[i] = pos[medianIndex];
pos[medianIndex] = tmp;
}
shift = step;
}
return left;
} /* findMedianOfMedians */
int findMedianIndex(int A[], int m, int B[], int n, int k)
{
if(0==m)
{
return B[k-1];
}
if(0==n)
{
return A[k-1];
}
if(1==k)
{
return min(A[0], B[0]);
}
int i=min(m,k/2);
int j=min(n,k/2);
if(A[i-1]<B[j-1])
{
return findMedianIndex(A+i,m-i,B,n,k-i);
}
return findMedianIndex(A,m,B+j,n-j,k-j);
}
//Computes the median of each group of 5 elements and stores
//it as the first element of the group. Recursively does this
//till there is only one group and hence only one Median
double findMedianOfMedians(int rows, int cols, int colToSortOn, double * array,
int left, int right)
{
double * colToSort = array+colToSortOn*rows;
if(left == right)
return colToSort[left];
int i, shift = 1;
while(shift <= (right - left)) {
for(i = left; i <= right; i+=shift*5) {
int endIndex = (i + shift*5 - 1 < right) ? i + shift*5 - 1 : right;
int medianIndex = findMedianIndex(rows, cols, colToSortOn, array,
i, endIndex, shift);
swapRows(rows, cols, array, i, medianIndex);
}
shift *= 5;
}
return colToSort[left];
}
