[leetcode] 885. Spiral Matrix III

[leetcode] 885. Spiral Matrix III

Description

On a 2 dimensional grid with R rows and C columns, we start at (r0, c0) facing east.

Here, the north-west corner of the grid is at the first row and column, and the south-east corner of the grid is at the last row and column.

Now, we walk in a clockwise spiral shape to visit every position in this grid.

Whenever we would move outside the boundary of the grid, we continue our walk outside the grid (but may return to the grid boundary later.)

Eventually, we reach all R * C spaces of the grid.

Return a list of coordinates representing the positions of the grid in the order they were visited.

Example 1:

Input: R = 1, C = 4, r0 = 0, c0 = 0Output: [[0,0],[0,1],[0,2],[0,3]]

Example 2:

Input: R = 5, C = 6, r0 = 1, c0 = 4Output: [[1,4],[1,5],[2,5],[2,4],[2,3],[1,3],[0,3],[0,4],[0,5],[3,5],[3,4],[3,3],[3,2],[2,2],[1,2],[0,2],[4,5],[4,4],[4,3],[4,2],[4,1],[3,1],[2,1],[1,1],[0,1],[4,0],[3,0],[2,0],[1,0],[0,0]]

Note:

1 <= R <= 1001 <= C <= 1000 <= r0 < R0 <= c0 < C

分析

题目的意思是：从指定位置遍历螺旋矩阵。这道题我一开始想复杂了，后面发现挺简单的，按照题目的要求从指定位置先向右，再向下，再向左，再向上就行了。注意用step变量控制在该方向上遍历的数目。

代码

class Solution: def add(self,res,R,C,x,y): if(x<0 or x>=R or y<0 or y>=C): return res.append([x,y]) def spiralMatrixIII(self, R: int, C: int, r0: int, c0: int) -> List[List[int]]: res=[] step=1 while(len(res)

参考文献

​​【中规中矩】两种解法​​

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