This is the Matrix Rotation problem from hackerrank.com.
You are given a 2D matrix, \$a\$, of dimension \$M×N\$ and a positive integer \$R\$. You have to rotate the matrix R times and print the resultant matrix. Rotation should be in anti-clockwise direction.
Rotation of a \$4×5\$ matrix is represented by the following figure. Note that in one rotation, you have to shift elements by one step only (refer sample tests for more clarity).
It is guaranteed that the minimum of \$M\$ and \$N\$ will be even.
Input
First line contains three space separated integers, \$M\$, \$N\$ and \$R\$, where \$M\$ is the number of rows, \$N\$ is number of columns in matrix, and \$R\$ is the number of times the matrix has to be rotated. Then \$M\$ lines follow, where each line contains \$N\$ space separated positive integers. These \$M\$ lines represent the matrix.
Output
Print the rotated matrix.
Constraints
- \$2 \le M, N \le 300\$
- \$1 \le R \le 10^9\$
- \$\min(M, N) ≡ 0 \pmod 2\$
- \$1 \le a_{ij} \le 10^8\$, where \$i \in [1\ldots M]\$ and \$j \in [1\ldots N]\$
Sample Input #00
4 4 1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Sample Output #00
2 3 4 8 1 7 11 12 5 6 10 16 9 13 14 15
Sample Input #01
4 4 2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Sample Output #01
3 4 8 12 2 11 10 16 1 7 6 15 5 9 13 14
Following is how I tried to solve the problem, but it runs just too slow:
from copy import deepcopy
aM, aN, R = map(int, input().split())
pivots = min(aM, aN)//2
refMat = []
baseMat = []
for i in range(aM):
readInput = list(map(int, input().split()))
baseMat.append(readInput)
refMat = deepcopy(baseMat)
for i in range(pivots):
cLimit = (aN - 1) - i
rLimit = (aM - 1) - i
loopLength = (aM + aN - 2 - 4*i)*2
nbrOfRotations = R%loopLength
for rotnIndex in range(nbrOfRotations):
# Corner movements
# Pivot
refMat[i][i] = baseMat[i][i + 1]
# Column End
refMat[i][cLimit] = baseMat[i + 1][cLimit]
# Row End
refMat[rLimit][i] = baseMat[rLimit - 1][i]
# Pivot diagonal
refMat[rLimit][cLimit] = baseMat[rLimit][cLimit - 1]
# Top movement
for j in range(i+1, cLimit):
refMat[i][j] = baseMat[i][j + 1]
# Bottom movement
for j in range(i+1, cLimit):
refMat[rLimit][j] = baseMat[rLimit][j - 1]
# Left movement
for j in range(i+1, rLimit):
refMat[j][i] = baseMat[j - 1][i]
# Right movement
for j in range(i+1, rLimit):
refMat[j][cLimit] = baseMat[j + 1][cLimit]
baseMat = deepcopy(refMat)
for i in refMat:
for e in i:
print(e, end = " ")
print()
Note: No advanced libraries such as NumPy, SciPy etc. are allowed. However, I would love to know if they offer a better workaround.
rows = 136, columns = 240 and rotations = 212131
\$\endgroup\$