[LeetCode]题解（python）：054-Spiral Matrix

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题目来源

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https://leetcode.com/problems/spiral-matrix/

Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order.

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题意分析

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Input: a matrix

Output: a list

Conditions: 蛇形输出

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题目思路

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自己本来在想有没有一些不一样的算法，然后发现直接右下左上顺序做就好了，看到一个博客的分类做得不错，重点是要看边界情况，直接看代码。

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AC代码（Python）

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class Solution(object):
    def spiralOrder(self, matrix):
        """
        :type matrix: List[List[int]]
        :rtype: List[int]
        """
        if matrix == []:
            return []
        up = 0
        left = 0
        down = len(matrix) - 1
        right = len(matrix[0]) - 1

        direct = 0

        res = []

        while True:
            if direct == 0:
                for i in range(left, right + 1):
                    res.append(matrix[up][i])
                up += 1
            if direct == 1:
                for i in range(up, down + 1):
                    res.append(matrix[i][right])
                right -= 1
            if direct == 2:
                for i in range(right, left - 1, -1):
                    res.append(matrix[down][i])
                down -= 1
            if direct == 3:
                for i in range(down, up -1, -1):
                    res.append(matrix[i][left])
                left += 1
            if up > down or  left > right:
                return res
            direct = (direct + 1) % 4