spiraltraverse.java

import java.io.*;
import java.util.*;

public class Solution {
  
    public static final int RIGHT = 1;
    public static final int LEFT = 2;
    public static final int DOWN = 3;
    public static final int UP = 4;
  
    /**
     * This method should print a 2D integer array in spiral order, clockwise
     *
     * @param matrix 2D array of integers to traverse over
     *
     */
    public static void spiralTraverse(int matrix[][]) {
        int colLen = matrix[0].length;
        int rowLen = matrix.length;
        int row = 0;
        int col = 0;
      
        boolean traversing = true;
        int dir = RIGHT;
      
        int colMinBound = -1, colMaxBound = colLen, 
            rowMinBound = -1, rowMaxBound = rowLen;
      
        System.out.println(matrix[row][col]);
        
        int newCol = col + (dir == RIGHT ? 1 : 0) - (dir == LEFT ? 1 : 0);
        int newRow = row + (dir == DOWN ? 1 : 0) - (dir == UP ? 1 : 0);
      
        while(traversing) {
          
          if(newCol == colMinBound) { // hit boundary while going left
            rowMaxBound = row;
            dir = UP;
          } else if(newCol == colMaxBound) { // hit boundary while going right
            rowMinBound = row;
            dir = DOWN;
          } else if(newRow == rowMinBound) { // hit boundary while going up
            colMinBound = col;
            dir = RIGHT;
          } else if(newRow == rowMaxBound) { // hit boundary while going down
            colMaxBound = col;
            dir = LEFT;
          } else {
            col = newCol;
            row = newRow;
            System.out.println(matrix[row][col]);
          }
          
          newCol = col + (dir == RIGHT ? 1 : 0) - (dir == LEFT ? 1 : 0);
          newRow = row + (dir == DOWN ? 1 : 0) - (dir == UP ? 1 : 0);
          
          // detect if spiral traveral is finished-
          // if difference between boundries is 1, nowwhere to go
          if(rowMaxBound - rowMinBound == 1 || colMaxBound - colMinBound == 1){
            traversing = false;
          }
      }
    }

    public static void main(String[] args) {
        // int EXAMPLE_MATRIX[][] = { {1,2,3}, {4,5,6}, {7,8,9} };  
        // int EXAMPLE_MATRIX[][] = { {1,2,3,4}, {5,6,7,8}, {9,10,11,12}, {13,14,15,16} };  
        int EXAMPLE_MATRIX[][] = { {1, 2}, {3, 4}, {5, 6}, {7, 8} };
      
        spiralTraverse(EXAMPLE_MATRIX);
    }
}

/*
[
  [ 1, 2, 3, 4],
  [ 5, 6, 7, 8],
  [ 9,10,11,12],
  [13,14,15,16]
]

[
  [ 1, 2, 3, 4, 0, 0],
  [ 5, 6, 7, 8, 0, 0],
  [ 9,10,11,12, 0, 0],
  [13,14,15,16, 0, 0],
  [13,14,15,16, 0, 0],
  [13,14,15,16, 0, 0]
]
*/

// row 0 col 9
// row 1 col 8