【LeetCode】54. 螺旋矩阵

1 问题

给你一个 m 行 n 列的矩阵 matrix ，请按照 顺时针螺旋顺序 ，返回矩阵中的所有元素。

示例 1：

输入：matrix = [[1,2,3],[4,5,6],[7,8,9]]
输出：[1,2,3,6,9,8,7,4,5]

示例 2：

输入：matrix = [[1,2,3,4],[5,6,7,8],[9,10,11,12]]
输出：[1,2,3,4,8,12,11,10,9,5,6,7]

2 答案

这题直接不会

再次尝试修改

class Solution:
    def spiralOrder(self, matrix: List[List[int]]) -> List[int]:
        up = 0
        down = len(matrix) - 1
        left = 0
        right = len(matrix[0]) - 1
        res = []
        curx = 0
        cury = 0
        move = [(1,0), (0,1), (-1,0), (0,-1)]
        add = 0
        # 从结果出发，去寻找while的条件比较容易
        while len(res) != (len(matrix)) * (len(matrix[0])):
            res.append(matrix[cury][curx])
            if curx == right and cury == up and add == 0:                
                up += 1
                add += 1
            if cury == down and curx == right and add == 1:
                right -= 1
                add += 1
            if curx == left and cury == down and add == 2:
                down -= 1
                add += 1
            if cury == up and curx == left and add == 3:
                left += 1
                add += 1
            add %= 4
            curx+=move[add][0]
            cury+=move[add][1]
        return res
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官方解， 顺时针旋转矩阵：先转置，再上下翻转。逆时针旋转矩阵：先上下翻转，再转置。

class Solution:
    def spiralOrder(self, matrix: List[List[int]]) -> List[int]:
        res = []
        while matrix:
            res += matrix.pop(0)  # pop 默认返回最后一个元素
            matrix = list(map(list, zip(*matrix)))[::-1]  # [::-1] 上下翻转
        return res
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https://leetcode.cn/problems/spiral-matrix/solutions/24232/na-yi-xing-ni-shi-zhen-zhuan-yi-xia-by-suixin-3/

也可以直接遍历，但要确定好边界，遍历方向等细节问题

class Solution(object):
    def spiralOrder(self, matrix):
        M, N = len(matrix), len(matrix[0])
        left, right, up, down = 0, N - 1, 0, M - 1
        res = []
        x, y = 0, 0
        dirs = [(0, 1), (1, 0), (0, -1), (-1, 0)]
        cur_d = 0
        while len(res) != M * N:
            res.append(matrix[x][y])
            if cur_d == 0 and y == right:
                cur_d += 1
                up += 1
            elif cur_d == 1 and x == down:
                cur_d += 1
                right -= 1
            elif cur_d == 2 and y == left:
                cur_d += 1
                down -= 1
            elif cur_d == 3 and x == up:
                cur_d += 1
                left += 1
            cur_d %= 4  # 4个方向，所以是4
            x += dirs[cur_d][0]
            y += dirs[cur_d][1]
        return res
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https://leetcode.cn/problems/spiral-matrix/solutions/656925/ju-zhen-bian-li-wen-ti-de-si-bu-qu-by-fu-91za/