54.md

54. 螺旋矩阵

也可以称为 顺时针打印矩阵

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

思路

• 四边有栏，栏往里缩

代码

class Solution {
    public List<Integer> spiralOrder(int[][] matrix) {
        if (matrix.length == 0) {
            return new ArrayList<>();
        }
        int left = 0, right = matrix[0].length - 1, top = 0, bottom = matrix.length - 1;
        List<Integer> res = new ArrayList<>();
        while (true) {
            for (int i = left; i <= right; i++) {
                res.add(matrix[top][i]);
            }
            if (++top > bottom) break;
            for (int i = top; i <= bottom; i++) {
                res.add(matrix[i][right]);
            }
            if (--right < left) break;
            for (int i = right; i >= left; i--) {
                res.add(matrix[bottom][i]);
            }
            if (--bottom < top) break;
            for (int i = bottom; i >= top; i--) {
                res.add(matrix[i][left]);
            }
            if (++left > right) break;
        }
        return res;
    }
}

二维数组

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

matrix[0] = [1,2,3]  x = 0