1260. Shift 2D Grid - Explanation

class Solution:
    def shiftGrid(self, grid: List[List[int]], k: int) -> List[List[int]]:
        m, n = len(grid), len(grid[0])

        while k:
            cur = [[0] * n for _ in range(m)]

            for r in range(m):
                for c in range(n - 1):
                    cur[r][c + 1] = grid[r][c]

            for r in range(m):
                cur[(r + 1) % m][0] = grid[r][n - 1]

            grid = cur
            k -= 1

        return grid

class Solution:
    def shiftGrid(self, grid: List[List[int]], k: int) -> List[List[int]]:
        m, n = len(grid), len(grid[0])

        while k:
            prev = grid[m - 1][n - 1]
            for r in range(m):
                for c in range(n):
                    grid[r][c], prev = prev, grid[r][c]
            k -= 1

        return grid

class Solution:
    def shiftGrid(self, grid: List[List[int]], k: int) -> List[List[int]]:
        m, n = len(grid), len(grid[0])
        N = m * n
        k %= N

        arr = [0] * N
        for r in range(m):
            for c in range(n):
                arr[r * n + c] = grid[r][c]

        def reverse(l, r):
            while l < r:
                arr[l], arr[r] = arr[r], arr[l]
                l += 1
                r -= 1

        reverse(0, N - 1)
        reverse(0, k - 1)
        reverse(k, N - 1)

        for r in range(m):
            for c in range(n):
                grid[r][c] = arr[r * n + c]

        return grid

class Solution:
    def shiftGrid(self, grid: List[List[int]], k: int) -> List[List[int]]:
        M, N = len(grid), len(grid[0])

        def posToVal(r, c):
            return r * N + c

        def valToPos(v):
            return [v // N, v % N]

        res = [[0] * N for _ in range(M)]
        for r in range(M):
            for c in range(N):
                newVal = (posToVal(r, c) + k) % (M * N)
                newR, newC = valToPos(newVal)
                res[newR][newC] = grid[r][c]

        return res