/* A recursive function to get the median of ar1[] and ar2[]
using binary search */
int getMedianRec(int ar1[], int ar2[], int left, int right, int n)
{
int i, j;
/* We have reached at the end (left or right) of ar1[] */
if (left > right)
return getMedianRec(ar2, ar1, 0, n-1, n);
i = (left + right)/2;
j = n - i - 1; /* Index of ar2[] */
/* Recursion terminates here.*/
if (ar1[i] > ar2[j] && (j == n-1 || ar1[i] <= ar2[j+1]))
{
/* ar1[i] is decided as median 2, now select the median 1
(element just before ar1[i] in merged array) to get the
average of both*/
if (i == 0 || ar2[j] > ar1[i-1])
return (ar1[i] + ar2[j])/2;
else
return (ar1[i] + ar1[i-1])/2;
}
/*Search in left half of ar1[]*/
else if (ar1[i] > ar2[j] && j != n-1 && ar1[i] > ar2[j+1])
return getMedianRec(ar1, ar2, left, i-1, n);
/*Search in right half of ar1[]*/
else /* ar1[i] is smaller than both ar2[j] and ar2[j+1]*/
return getMedianRec(ar1, ar2, i+1, right, n);
}
int getMedianRec(int a[], int b[], int left, int right, int n){
int i, j;
if(left > right)
return getMedianRec(b, a, 0, n-1, n);
i = (left + right)/2;
j = n - i - 1;
if(b[j] < a[i] && (j == n-1 || a[i] <= b[j+1])){
if(i == 0 || b[j] > a[i-1])
return (a[i] + b[j])/2;
else return (a[i] + a[i-1])/2;
}
else if(a[i] > b[j] && j != n-1 && a[i] > b[j+1]){
return getMedianRec(a, b, left, i-1, n);
}
else return getMedianRec(a, b, i+1, right, n);
}
/* This function returns median of ar1[] and ar2[].
Assumptions in this function:
Both ar1[] and ar2[] are sorted arrays
Both have n elements */
int getMedian(int ar1[], int ar2[], int n)
{
// If all elements of array 1 are smaller then
// median is average of last element of ar1 and
// first element of ar2
if (ar1[n-1] < ar2[0])
return (ar1[n-1]+ar2[0])/2;
// If all elements of array 1 are smaller then
// median is average of first element of ar1 and
// last element of ar2
if (ar2[n-1] < ar1[0])
return (ar2[n-1]+ar1[0])/2;
return getMedianRec(ar1, ar2, 0, n-1, n);
}
int getMedian(int a[], int b[], int n){
return getMedianRec(a, b, 0, n-1, n);
}
/* This function returns median of ar1[] and ar2[].
Assumptions in this function:
Both ar1[] and ar2[] are sorted arrays
Both have n elements */
int getMedian(int ar1[], int ar2[], int n)
{
return getMedianRec(ar1, ar2, 0, n-1, n);
}
