[54]螺旋矩阵

//给你一个 m 行 n 列的矩阵 matrix ，请按照 顺时针螺旋顺序 ，返回矩阵中的所有元素。 
//
// 
//
// 示例 1： 
//
// 
//输入：matrix = [[1,2,3],[4,5,6],[7,8,9]]
//输出：[1,2,3,6,9,8,7,4,5]
// 
//
// 示例 2： 
//
// 
//输入：matrix = [[1,2,3,4],[5,6,7,8],[9,10,11,12]]
//输出：[1,2,3,4,8,12,11,10,9,5,6,7]
// 
//
// 
//
// 提示： 
//
// 
// m == matrix.length 
// n == matrix[i].length 
// 1 <= m, n <= 10 
// -100 <= matrix[i][j] <= 100 
// 
// Related Topics 数组 
// 👍 620 👎 0

/*
* 54 螺旋矩阵
* 2021-03-01 14:33:36
* @author oxygenbytes
*/ 
#include "leetcode.h" 
//leetcode submit region begin(Prohibit modification and deletion)
class Solution {
public:
    vector<int> spiralOrder(vector<vector<int>>& matrix) {
        if(matrix.empty() || matrix[0].empty()) return {};
        int m = matrix.size();
        int n = matrix[0].size();

        vector<int> ans;
        int d = 1;
        int i = 0, j = 0;
        int dx[4] = {-1, 0, 1, 0};
        int dy[4] = {0, 1, 0, -1};
        for(int k = 0;k < m * n;k++){
            ans.push_back(matrix[i][j]);
            matrix[i][j] = 0;
            int a = i + dx[d];
            int b = j + dy[d];
            if(a < 0 || a >= m || b < 0 || b >= n || matrix[a][b] == 0){
                d = (d + 1) % 4;
                a = i + dx[d];
                b = j + dy[d];
            }
            i = a, j = b;
        }

        return ans;
    }
};
//leetcode submit region end(Prohibit modification and deletion)