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
# Python 3 program to print# matrix in anti-spiral formR = 4C = 5def antiSpiralTraversal(m, n, a): k = 0 l = 0 # k - starting row index # m - ending row index # l - starting column index # n - ending column index # i - iterator stk = [] while (k <= m and l <= n): # Print the first row # from the remaining rows for i in range(l, n + 1): stk.append(a[k][i]) k += 1 # Print the last column # from the remaining columns for i in range(k, m + 1): stk.append(a[i][n]) n -= 1 # Print the last row # from the remaining rows if ( k <= m): for i in range(n, l - 1, -1): stk.append(a[m][i]) m -= 1 # Print the first column # from the remaining columns 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()# Driver Codemat = [[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)# This code is contributed# by ChitraNayal |
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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