leetcode -- Spiral Matrix II

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 ]
]

java 中是传值的，将count作为返回值返回

public static int[][] generateMatrix(int n) {
        // Start typing your Java solution below
        // DO NOT write main() function
        if(n <= 0)
            return new int[0][];
        
        int rows = n;
        int cols = n;
        int[][] result = new int[n][n];
        int count = 1;
        
        int start = 0;
        while (rows > start * 2 && cols > start * 2) {
            count = printCircle(result, rows, cols, start, count, n * n);
            start++;
        }
        
        return result;
    }
    
    public static int printCircle(int[][] matrix, int rows, int cols,
            int start, int count, int n) {
        int endX = cols - 1 - start;
        int endY = rows - 1 - start;

        // print row
        for (int i = start; i <= endX && count <= n; i++) {
            matrix[start][i] = count ++;
        }

        // print col
        if (endY > start) {
            for (int i = start + 1; i <= endY && count <= n; i++) {
                matrix[i][endX] = count ++;
            }
        }
        // print row
        if (endX > start && endY > start) {
            for (int i = endX - 1; i >= start && count <= n; i--) {
                matrix[endY][i] = count ++;
            }
        }
        // print col
        if (endX > start && endY - 1 > start) {
            for (int i = endY - 1; i > start && count <= n; i--) {
                matrix[i][start] = count ++;
            }
        }
        return count;
    }