python剑指offer 顺时针打印指针

题目描述

输入一个矩阵，按照从外向里以顺时针的顺序依次打印出每一个数字，例如，如果输入如下4 X 4矩阵： 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 则依次打印出数字1,2,3,4,8,12,16,15,14,13,9,5,6,7,11,10.

# -*- coding:utf-8 -*-
class Solution:
    # matrix类型为二维列表，需要返回列表
    def printMatrix(self, matrix):
        # write code here
        if not matrix:
            return None
        rows = len(matrix)
        cols = len(matrix[0])
        start = 0
        result = []
        while rows > 2*start and cols > 2*start:
            endx = rows-1-start
            endy = cols-1-start
            for i in range(start,endy+1):
                result.append(matrix[start][i])
            if start < endx:
                for i in range(start+1,endx+1):
                    result.append(matrix[i][endy])
            if start < endx and start < endy:
                for i in range(endy-1,start-1,-1):
                    result.append(matrix[endx][i])
            if start < endx-1 and start < endy:
                for i in range(endx-1,start,-1):
                    result.append(matrix[i][start])
                     
            start += 1
        return result