排序与查找

1，快排

void QuickSort( int a[] , int low , int high )
{
    int i = low , j = high ;
    int temp = a[i] ;
    while( i < j )
    {
        while( i < j  && temp <= a[j] )j-- ;
        if( i < j )
        {
            a[i] = a[j] ;
            i++ ;
        }

        while( i < j && a[i] < temp ) i++ ;
        if( i < j )
        {
            a[j] = a[i] ;
            j-- ;
        }
    }

    a[i] = temp ;

    if( low < i )
        QuickSort( a , low , i - 1 ) ;
    if( i < high )
        QuickSort( a , i + 1 , high ) ;
}

2，堆排

template <class T >
void /*MinHeap<T>::*/FilterDown( T heapArray[] , int i , int heapSize )
{
    int currentPos , childPos ;
    T target ;

    currentPos = i ;//当前节点
    target = heapArray[i] ;

    childPos = 2*currentPos + 1 ;//当前节点的左孩子节点

    while( childPos < heapSize )
    {
        if(  childPos + 1 < heapSize &&  heapArray[ childPos + 1 ] < heapArray[ childPos ] )
            childPos++ ;

        if( target <= heapArray[ childPos ] )
            break; 
        else
        {
            heapArray[ currentPos ] = heapArray[ childPos ] ;
            currentPos = childPos ;
            childPos = 2*currentPos + 1 ;
        }

    }

    heapArray[currentPos]  = target ;

}

//堆化
template<class T>
/*MinHeap<T>::*/MinHeap( T arr[] , n )
{
    if( n <= 0 )
    {
        exit(0) ;
    }

    int currentPos = ( n - 1 )/2 ;
    while( currentPos > = 0  )
    {
        FilterDown( arr , currentPos , n ) ;
    }

}


void HeapSort( int a[] , int n )
{
    int temp ;
    MinHeap( a , n ) ;
    for( int i = n-1 ; i >0 ; i --  )
    {
        temp = a[0] ;
        a[0] = a[i] ;//把最后一个元素放到堆顶
        a[i] = temp ;//把第一个元素放到最后

        FilterDown( a , 0 , i-1  ) ;//调整跟节点满足最小堆
    }
}