数组Array

数组Array是最基本的数据结构，在内存中为一段定长连续内存,很多编程语言都有实现。

一、一维数组

下面代码实现了一维数组和它的遍历。

clear并非清空数组，而是采用具体值对数组进行初始化。

import ctypes
 
class Array :
    def __init__( self, size ):
        assert size > 0, "Array size must be > 0"
        self._size = size
        PyArrayType = ctypes.py_object * size
        self._elements = PyArrayType()
        self.clear( None )
    def __len__( self ):
        return self._size
    def __getitem__( self, index ):
        assert index >=0 and index < len(self), "Array subscript out of range"
        return self._elements[ index ]
    def __setitem__( self, index, value ):
        assert index >=0 and index < len(self), "Array subscript out of range"
        self._elements[ index ] = value
    def clear( self, value ):
        for i in range( len(self) ) :
            self._elements[i] = value
    def __iter__( self ):
        return _ArrayIterator( self._elements )

class _ArrayIterator :
    def __init__( self, theArray ):
        self._arrayRef = theArray
        self._curNdx = 0
 
    def __iter__( self ):
        return self
 
    def __next__( self ):
        if self._curNdx < len( self._arrayRef ) :
            entry = self._arrayRef[ self._curNdx ]
            self._curNdx += 1
            return entry
        else :
            raise StopIteration
 
if __name__=='__main__':
    myarray=Array(5)
    myarray.clear(1)
    myarray.__setitem__(2,5)
    print myarray.__getitem__(2)
    it=myarray.__iter__()
    while True:
        try:
            print it.__next__()
        except StopIteration:
            break

二、二维数组

二维数组的构造基于一维数组Array，它可以看做是一个以行数为size的一维数组，区别在于数组中的每个元素并不是具体的值，而是由以列数为size的数组构成。如下图所示：

class Array2D :
    def __init__( self, numRows, numCols ):
        self._theRows = Array( numRows )
        for i in range( numRows ) :
            self._theRows[i] = Array( numCols )
    def numRows( self ):
        return len( self._theRows )
    def numCols( self ):
        return len( self._theRows[0] )
def __getitem__( self, ndxTuple ):
        assert len(ndxTuple) == 2, "Invalid number of array subscripts."
        row = ndxTuple[0]
        col = ndxTuple[1]
        assert row >=0 and row < self.numRows() and col >=0 and col < self.numCols(), "Array subscript out of range."
        the1dArray = self._theRows[row]
        return the1dArray[col]
    def __setitem__( self, ndxTuple, value ):
        assert len(ndxTuple) == 2, "Invalid number of array subscripts."
        row = ndxTuple[0]
        col = ndxTuple[1]
        assert row >=0 and row < self.numRows() and col >=0 and col < self.numCols(), "Array subscript out of range."
        the1dArray = self._theRows[row]
        the1dArray[col] = value