牛客网：NC38 螺旋矩阵

import java.util.ArrayList;
import java.util.List;

/**
 * @author xienl
 * @description 螺旋矩阵
 * @date 2022/7/6
 */

public class Solution {
    public static void main(String[] args) {
        Solution solution = new Solution();

    }

    public ArrayList<Integer> spiralOrder(int[][] matrix) {
        if (matrix.length == 0){
            return new ArrayList<>();
        }
        int m = matrix.length, n = matrix[0].length;
        int[][] directions = {{0, 1}, {1,0},{-1, 0}, {0, -1}};
        int direction = 0;
        int row = 0;
        int col = 0;
        ArrayList<Integer> list = new ArrayList<>();
        boolean[][] visited = new boolean[m][n];

        for (int i = 0; i < m * n; i++){
            list.add(matrix[row][col]);
            visited[row][col] = true;
            int nextRow = row + directions[direction][0];
            int nextCol = col + directions[direction][1];
            if (nextCol < 0 || nextRow >= m || nextCol >= n || visited[nextRow][nextCol]){
                direction = (direction + 1) % 4;
            }
            row = row + directions[direction][0];
            col = col + directions[direction][1];
        }
        return list;
    }
}