The O (N) algorithm and kmin algorithm of C + + to find median number _c language

This article describes the C + + to find the median O (N) algorithm and kmin algorithm, shared for everyone to reference. The specific methods are as follows:

The search algorithm for the median of O (N) time by using the fast sort partition operation is as follows:

#include <iostream> #include <cassert> #include <algorithm> #include <iterator> using namespace

Std
int array[] = {1, 2, 10, 8, 9, 7, 5};

const int size = sizeof array/sizeof *array;

 int partition (int *array, int left, int right) {if (array = = NULL) return-1;
 int pos = right;
 right--;

 while (left <= right) {while (Left < POS && Array[left] <= Array[pos]) left++;

 while (right >= 0 && array[right] > Array[pos]) right--;

 if (left >= right) break;
 Swap (Array[left], array[right]);

 } swap (Array[left], Array[pos]);
return to left;

 int getmidindex (int *array, int size) {if (array = NULL | | size <= 0) return-1;
 int left = 0;
 int right = size-1;
 int midpos = right >> 1;

 int index =-1;

 while (index!= midpos) {index = partition (array, left, right);
 if (Index < Midpos) {left = index + 1;
 else if (Index > Midpos) {right = Index-1;
 } else {break;

}
 } ASSERT (index = = Midpos);
return Array[index];

 } void Main () {int value = Getmidindex (array, size);

 cout << "Value:" << value << Endl;}

The search Kmin algorithm is as follows:

int findkmin (int *array, int size, int k)
{
 if (array = NULL | | size <= 0)
 return-1;

 int left = 0;
 int right = size-1;
 int index =-1;

 while (index!= k)
 {
 index = partition (array, left, right);

 if (Index < k)
 {left
  = index + 1;
 }
 else if (Index > K)
 {right
  = index-1;
 } 
 Else
 {break
  ;
 }
 }

 ASSERT (index = = k);
 return array[index];
}

I hope this article is helpful to the learning of C + + program algorithm design.