Spiral Matrix

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].

 public static ArrayList spiralOrder(int[][] matrix) {
        // Start typing your Java solution below
        // DO NOT write main() function
        ArrayList res = new ArrayList();
        if (matrix.length == 0) {
            return res;
        }
        
        int colStart = 0;
        int colEnd = matrix[0].length - 1;
        int rowStart = 0;
        int rowEnd = matrix.length - 1;
        
        while (colStart <= colEnd && rowStart <= rowEnd) {
            for (int i=colStart; i<=colEnd; i++) {
                res.add(matrix[rowStart][i]);
            }
            rowStart++;
            for (int i=rowStart; i<=rowEnd; i++) {
                res.add(matrix[i][colEnd]);
            }
            colEnd--;
            if (rowStart > rowEnd) break;
            for (int i=colEnd; i>=colStart; i--) {
                res.add(matrix[rowEnd][i]);
            }
            rowEnd--;
            if (colStart > colEnd) break;
            for (int i=rowEnd; i>=rowStart; i--) {
                res.add(matrix[i][colStart]);
            }
            colStart++;
        }
        return res;
    }

Given an integer n, generate a square matrix filled with elements from 1 to n² in spiral order.

For example,
Given n = 3,

You should return the following matrix:

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

public class Solution {
    public int[][] generateMatrix(int n) {
        // Start typing your Java solution below
        // DO NOT write main() function
        int[][] matrix = new int[n][n];
        int colStart = 0;
        int colEnd = n - 1;
        int rowStart = 0;
        int rowEnd = n - 1;
        int val = 1;
        
        while (colStart <= colEnd && rowStart <= rowEnd) {
            for (int i = colStart; i <= colEnd; i++) {
                matrix[rowStart][i] = val;
                val++;
            }
            
            rowStart++;
            
            for (int i = rowStart; i <= rowEnd; i++) {
                matrix[i][colEnd] = val;
                val++;
            }
            
            colEnd--;
            
            for (int i = colEnd; i >= colStart; i--) {
                matrix[rowEnd][i] = val;
                val++;
            }
            
            rowEnd--;
            
            for (int i = rowEnd; i >= rowStart; i--) {
                matrix[i][colStart] = val;
                val++;
            }
            
            colStart++;
        }
        return matrix;
    }
}