16.1 Spiral Order Matrix I (Medium)

Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order.

For example,

Given the following matrix:

[

[ 1, 2, 3 ],

[ 4, 5, 6 ],

[ 7, 8, 9 ]

]

You should return

[1,2,3,6,9,8,7,4,5].

https://leetcode.com/problems/spiral-matrix/

public class Solution {
    public List<Integer> spiralOrder(int[][] matrix) {
        ArrayList<Integer> result = new ArrayList<Integer>();

        if(matrix==null||matrix.length==0||matrix[0].length==0) return result;

        int top=0;
        int left=0;
        int bottom=matrix.length-1;
        int right=matrix[0].length-1;
        int direction =0;

        while(top<=bottom && left<=right){

            if(direction==0){       //move right
                for(int i=left;i<=right;i++){
                    result.add(matrix[top][i]);
                }
                top++;
                direction=1;
            }
            else if(direction==1){  //move down
                for(int i=top;i<=bottom;i++){
                    result.add(matrix[i][right]);
                }
                right--;
                direction=2;
            }
            else if(direction==2){  //move left
                for(int i=right;i>=left;i--){
                    result.add(matrix[bottom][i]);
                }
                bottom--;
                direction=3;
            }
            else if(direction==3){  //move up
                for(int i=bottom;i>=top;i--){
                    result.add(matrix[i][left]);
                }
                left++;
                direction=0;
            }



        }

        return result;
    }
}