螺旋遍历二维数组

/* 
 * 思路：
 * 1. 使用传统的方式构建一个螺旋遍历的列表。
 * 2. 将这个列表转化为Java Stream进行处理。
 */
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.IntStream;

public class SpiralOrderStream {
    public List<Integer> spiralOrder(int[][] matrix) {
        List<Integer> result = new ArrayList<>();
        if (matrix == null || matrix.length == 0) return result;
        int top = 0, bottom = matrix.length - 1;
        int left = 0, right = matrix[0].length - 1;

        while (top <= bottom && left <= right) {
            IntStream.rangeClosed(left, right).forEach(i -> result.add(matrix[top][i]));
            top++;
            IntStream.rangeClosed(top, bottom).forEach(i -> result.add(matrix[i][right]));
            right--;
            if (top <= bottom) IntStream.rangeClosed(left, right).map(i -> right - i + left).forEach(i -> result.add(matrix[bottom][i]));
            bottom--;
            if (left <= right) IntStream.rangeClosed(top, bottom).map(i -> bottom - i + top).forEach(i -> result.add(matrix[i][left]));
            left++;
        }
        return result.stream().collect(Collectors.toList());
    }
}