[LeetCode]#1260. Shift 2D Grid

Environment: Python 3.7

Key technique: slice

Given a 2D grid of size m x n and an integer k. You need to shift the grid k times.

In one shift operation:

• Element at grid[i][j] moves to grid[i][j + 1].
• Element at grid[i][n - 1] moves to grid[i + 1][0].
• Element at grid[m - 1][n - 1] moves to grid[0][0].

Return the 2D grid after applying shift operation k times.

Example 1:

Input: grid = [[1,2,3],[4,5,6],[7,8,9]], k = 1
Output: [[9,1,2],[3,4,5],[6,7,8]]

Example 2:

Input: grid = [[3,8,1,9],[19,7,2,5],[4,6,11,10],[12,0,21,13]], k = 4
Output: [[12,0,21,13],[3,8,1,9],[19,7,2,5],[4,6,11,10]]

Example 3:

Input: grid = [[1,2,3],[4,5,6],[7,8,9]], k = 9
Output: [[1,2,3],[4,5,6],[7,8,9]]

Analysis:

1. Covert to matrix to list.
2. Calculate how to slice based on input k.
3. Combine slice result.
4. Convert list to matrix based on moving result.

Solution:

class Solution:
    def shiftGrid(self, grid, k):
        col=len(grid[0])
        nums=sum(grid,[])        
        k = k % len(nums)
        move=len(nums)-k
        ans=grid
        count=0
        nums = nums[move:] + nums[:move]
        for i in range(0,len(nums),col):
            ans[count]=nums[i:i+col]
            count+=1
        return ans

Lesson learn:

Matrix value will move to the same location when the k > list size. Use a simple % to calculate the impact move.

Submitted result:

Reference:

https://ithelp.ithome.com.tw/articles/10229264