a = [ 6 , 12 , 9 , 20 , 8 , 11 , 4 ]
for j in range( 1 , len( a ) ) :
if a[ j ] < a[ j - 1 ] :
a[ j ] = a[ j ] + a[ j - 1 ] ; a[ j - 1 ] = a[ j ] - a[ j - 1 ] ; a[ j ] = a[ j ] - a[ j - 1 ]
执行该段程序后,列表a的值是( )
lst = [2,5,2,1]
y = [1,1,1,1]
n = len(lst)
for i in range(①____):
for j in range(②____):
if ③____:
y[j] = y[j] + 1
else
y[i] = y[i] + 1
上述程序段3个划线处的表达式分别为( )