class Solution(object):
def rotate(self, matrix):
"""
:type matrix: List[List[int]]
:rtype: None Do not return anything, modify matrix in-place instead.
"""
n=len(matrix)
for i in xrange(n/2,n):
if i*2==n-1: continue
for j in xrange(n/2,n):
#print "({},{})=>({},{})=>({},{})=>({},{})".format(
# i, j, j, n-1-i, n-1-i, n-j-1, n-j-1, i)
matrix[j][n-1-i],matrix[n-1-i][n-j-1],matrix[n-j-1][i],matrix[i][j]=\
matrix[i][j],matrix[j][n-1-i],matrix[n-1-i][n-j-1],matrix[n-j-1][i]