Javascript Program to Print a given matrix in reverse spiral form
Given a 2D array, print it in reverse spiral form. We have already discussed Print a given matrix in spiral form. This article discusses how to do the reverse printing. See the following examples.
Input: 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: 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
Javascript
<script> // This is a modified code of // print-a-given-matrix-in-spiral-form/ let R = 3; let C = 6; // Function that print matrix in // reverse spiral form. function ReversespiralPrint(m, n, a) { // Large array to initialize it // with elements of matrix let b = new Array(100); /* k - starting row index l - starting column index*/ let i, k = 0, l = 0; // Counter for single dimension array //in which elements will be stored let z = 0; // Total elements in matrix let size = m*n; while (k < m && l < n) { // Variable to store value of matrix. let val; /* Print the first row from the remaining rows */ for (i = l; i < n; ++i) { // printf("%d ", a[k][i]); val = a[k][i]; b[z] = val; ++z; } k++; /* Print the last column from the remaining columns */ for (i = k; i < m; ++i) { // printf("%d ", a[i][n-1]); val = a[i][n-1]; b[z] = val; ++z; } n--; /* Print the last row from the remaining rows */ if ( k < m) { for (i = n-1; i >= l; --i) { // printf("%d ", a[m-1][i]); val = a[m-1][i]; b[z] = val; ++z; } m--; } /* Print the first column from the remaining columns */ if (l < n) { for (i = m-1; i >= k; --i) { // printf("%d ", a[i][l]); val = a[i][l]; b[z] = val; ++z; } l++; } } for (let i=size-1 ; i>=0 ; --i) { document.write(b[i] + " " ); } } /* Driver program to test above functions */ let a = [ [1, 2, 3, 4, 5, 6], [7, 8, 9, 10, 11, 12], [13, 14, 15, 16, 17, 18]]; ReversespiralPrint(R, C, a); </script> |
Output:
11 10 9 8 7 13 14 15 16 17 18 12 6 5 4 3 2 1
Time complexity: O(R*C) where R and C are no of rows and columns in given matrix
Auxiliary Space: O(1) because using constant space
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