Python Program to Print matrix in antispiral form
Last Updated :
19 Sep, 2022
Given a 2D array, the task is to print matrix in anti spiral form:
Examples:
Output: 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1
Input : arr[][4] = {1, 2, 3, 4
5, 6, 7, 8
9, 10, 11, 12
13, 14, 15, 16};
Output : 10 11 7 6 5 9 13 14 15 16 12 8 4 3 2 1
Input :arr[][6] = {1, 2, 3, 4, 5, 6
7, 8, 9, 10, 11, 12
13, 14, 15, 16, 17, 18};
Output : 11 10 9 8 7 13 14 15 16 17 18 12 6 5 4 3 2 1
The idea is simple, we traverse matrix in spiral form and put all traversed elements in a stack. Finally one by one elements from stack and print them.
Python 3
R = 4
C = 5
def antiSpiralTraversal(m, n, a):
k = 0
l = 0
stk = []
while (k < = m and l < = n):
for i in range (l, n + 1 ):
stk.append(a[k][i])
k + = 1
for i in range (k, m + 1 ):
stk.append(a[i][n])
n - = 1
if ( k < = m):
for i in range (n, l - 1 , - 1 ):
stk.append(a[m][i])
m - = 1
if (l < = n):
for i in range (m, k - 1 , - 1 ):
stk.append(a[i][l])
l + = 1
while len (stk) ! = 0 :
print ( str (stk[ - 1 ]), end = " " )
stk.pop()
mat = [[ 1 , 2 , 3 , 4 , 5 ],
[ 6 , 7 , 8 , 9 , 10 ],
[ 11 , 12 , 13 , 14 , 15 ],
[ 16 , 17 , 18 , 19 , 20 ]];
antiSpiralTraversal(R - 1 , C - 1 , mat)
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Output:
12 13 14 9 8 7 6 11 16 17 18 19 20 15 10 5 4 3 2 1
Time complexity: O(R + C).
Auxiliary Space: O(R + C).
Please refer complete article on Print matrix in antispiral form for more details!
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