剑指Offer 19. 顺时针打印矩阵 （其他）

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.

题目地址

https://www.nowcoder.com/practice/9b4c81a02cd34f76be2659fa0d54342a?tpId=13&tqId=11172&rp=3&ru=/ta/coding-interviews&qru=/ta/coding-interviews/question-ranking

思路

从左往右，再从上往下，再从右往左，最后从下往上遍历

Python

# -*- 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
        rows = len(matrix)
        cols = len(matrix[0])
        left, right = 0, cols-1
        top, bottom = 0, rows-1
        res = []
        while left <= right and top <= bottom:
            for i in range(left, right+1):
                res.append(matrix[top][i])
            for i in range(top+1,bottom+1):
                res.append(matrix[i][right])
            if top != bottom:
                for i in range(right-1,left-1,-1):
                    res.append(matrix[bottom][i])
            if left != right:
                for i in range(bottom-1,top,-1):
                    res.append(matrix[i][left])
            left += 1
            right -= 1
            top += 1
            bottom -= 1
        return res

if __name__ == '__main__':
    result = Solution().printMatrix([[1,2,3,4],[5,6,7,8],[9,10,11,12],[13,14,15,16]])
    print(result)