[LC] LEETCODE 54

[Rushia (みけねこ的鼻屎)]

https://leetcode.com/problems/spiral-matrix/description/
54. Spiral Matrix
給你一個用二維陣列表示的 m x n 的矩陣，返回他的所有元素（螺旋順序）。

Example 1
https://assets.leetcode.com/uploads/2020/11/13/spiral1.jpg
Input: matrix = [[1,2,3],[4,5,6],[7,8,9]]
Output: [1,2,3,6,9,8,7,4,5]

Example 2:
https://assets.leetcode.com/uploads/2020/11/13/spiral.jpg
Input: matrix = [[1,2,3,4],[5,6,7,8],[9,10,11,12]]
Output: [1,2,3,4,8,12,11,10,9,5,6,7]

思路：
1.遍歷陣列的時候不斷往某個方向前進，直到碰到邊界或碰到已經走過的地方就往下一個
  方向。

Java Code：
-----------------------------------------
class Solution {
    public List<Integer> spiralOrder(int[][] matrix) {
        List<Integer> res = new ArrayList<>();
        int m = matrix.length;
        int n = matrix[0].length;
        boolean[][] visited = new boolean[m][n];

        int y = 0;
        int x = 0;

        int[][] dirs = new int[][]{{0, 1}, {1, 0}, {0, -1}, {-1, 0}};
        int turn = 0;

        while (res.size() != m * n) {
            visited[y][x] = true;
            res.add(matrix[y][x]);
            int newY = y + dirs[turn][0];
            int newX = x + dirs[turn][1];
            if (newY < 0 || newY >= m || newX < 0 || newX >= n ||
visited[newY][newX]) {
                turn = (turn + 1) % 4;
                newY = y + dirs[turn][0];
                newX = x + dirs[turn][1];
            }
            y = newY;
            x = newX;
        }
        return res;
    }
}
-----------------------------------------

明天要上班 哭阿

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