算法导论中对于快速排序求中间值算法的疑惑~

public double medianOf3(int left, int right)

{

int center = (left+right)/2;

// order left & center

if( theArray[left] > theArray[center] )

swap(left, center);

// order left & right

if( theArray[left] > theArray[right] )

swap(left, right);

// order center & right

if( theArray[center] > theArray[right] )

swap(center, right);

swap(center, right-1); // put pivot on right

return theArray[right-1]; // return median value

} // end medianOf3()

 

为什么返回值是theArray[right-1]？