0.6 矩阵

[73. 矩阵置零](https://leetcode.cn/problems/set-matrix-zeroes/?envType=study-plan-v2&envId=top-100-liked)
```py
class Solution:
    def setZeroes(self, matrix: List[List[int]]) -> None:
        """
        Do not return anything, modify matrix in-place instead.
        """
        m, n = len(matrix), len(matrix[0])
        zero_row = set()
        zero_col = set()
        for i in range(m):
            for j in range(n):
                if matrix[i][j] == 0:
                    zero_col.add(j)
                    zero_row.add(i)
        for i in range(m):
            for j in range(n):
                if i in zero_row or j in zero_col:
                    matrix[i][j] = 0
```
[54. 螺旋矩阵](https://leetcode.cn/problems/spiral-matrix/?envType=study-plan-v2&envId=top-100-liked)
```py
class Solution:
    def spiralOrder(self, matrix: List[List[int]]) -> List[int]:
        m, n = len(matrix), len(matrix[0])
        res = []
        l, r, t, b = 0, n - 1, 0, m - 1
        while True:
            for i in range(l, r + 1):
                res.append(matrix[t][i])
            t += 1
            if t > b:
                break
            for i in range(t, b + 1):
                res.append(matrix[i][r])
            r -= 1
            if r < l:
                break
            for i in range(r, l - 1, -1):
                res.append(matrix[b][i])
            b -= 1
            if b < t:
                break
            for i in range(b, t - 1, -1):
                res.append(matrix[i][l])
            l += 1
            if l > r:
                break
        return res
```
[48. 旋转图像](https://leetcode.cn/problems/rotate-image/?envType=study-plan-v2&envId=top-100-liked)
```py
class Solution:
    def rotate(self, matrix: List[List[int]]) -> None:
        """
        Do not return anything, modify matrix in-place instead.
        """
        m, n = len(matrix), len(matrix[0])
        mid = m // 2
        for i in range(m):
            for j in range(i + 1, n):
                matrix[i][j], matrix[j][i] = matrix[j][i], matrix[i][j]

for i in range(m):
            for j in range(mid):
                matrix[i][j], matrix[i][n - 1 - j] = matrix[i][n - 1 - j], matrix[i][j]
```
[240. 搜索二维矩阵 II](https://leetcode.cn/problems/search-a-2d-matrix-ii/?envType=study-plan-v2&envId=top-100-liked)
```py
class Solution:
    def searchMatrix(self, matrix: List[List[int]], target: int) -> bool:
        m, n = len(matrix), len(matrix[0])
        row = 0
        col = n-1
        while row < m  and col >= 0:
            if target > matrix[row][col]:
                row += 1
            elif target < matrix[row][col]:
                col -= 1
            else:
                return True
        return False
```