Objective: This question was asked in Amazon interview for the Software development Engineer position, Write an algorithm to print all the elements of two dimensional array in spiral.
Example :
Input: Two dimensional array
Output: All array elements printed in spiral.
Approach:
- Start printing from first row.
- Print row and columns, forward and backward alternatively
- With every iteration of (either row or column), reduce the size of an row or column by 1
- Call recursively
Complete Code:
| public class Print2DArrayInSpiral { | |
| public int arrA[][] = { { 1, 2, 3, 4, 5 }, { 18, 19, 20, 21, 6 }, | |
| { 17, 28, 29, 22, 7 }, { 16, 27, 30, 23, 8 }, | |
| { 15, 26, 25, 24, 9 }, { 14, 13, 12, 11, 10 } }; | |
| public int printSpiral(int row_S, int row_E, int col_S, int col_E, | |
| boolean reverse, boolean rowPrint) { | |
| if (row_S > row_E && col_S > col_E) { | |
| return 1; | |
| } | |
| if (rowPrint == false) { | |
| if (reverse == false) { | |
| for (int i = col_S; i <= col_E; i++) { | |
| System.out.print(" " + arrA[row_S][i]); | |
| } | |
| } | |
| row_S++; | |
| rowPrint = true; | |
| reverse = false; | |
| } | |
| if (rowPrint == true) { | |
| if (reverse == false) { | |
| for (int i = row_S; i <= row_E; i++) { | |
| System.out.print(" " + arrA[i][col_E]); | |
| } | |
| } | |
| col_E—; | |
| rowPrint = false; | |
| reverse = true; | |
| } | |
| if (rowPrint == false) { | |
| if (reverse == true) { | |
| for (int i = col_E; i >= col_S; i—) { | |
| System.out.print(" " + arrA[row_E][i]); | |
| } | |
| } | |
| row_E—; | |
| rowPrint = true; | |
| reverse = true; | |
| } | |
| if (rowPrint == true) { | |
| if (reverse == true) { | |
| for (int i = row_E; i >= row_S; i—) { | |
| System.out.print(" " + arrA[i][col_S]); | |
| } | |
| } | |
| col_S++; | |
| rowPrint = false; | |
| reverse = false; | |
| } | |
| printSpiral(row_S, row_E, col_S, col_E, reverse, rowPrint); | |
| return 0; | |
| } | |
| public static void main(String args[]) { | |
| Print2DArrayInSpiral p = new Print2DArrayInSpiral(); | |
| p.printSpiral(0, 5, 0, 4, false, false); | |
| } | |
| } |
Output: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30