算法-矩阵-螺旋矩阵（按层模拟）

class Solution {
public:
    vector<int> spiralOrder(vector<vector<int>>& matrix) {
        //若空
        if(matrix.size() == 0 || matrix[0].size() == 0) return {};
        //行列
        int rows = matrix.size(), columns = matrix[0].size();
        //定义top,bottom,left,right
        int left = 0, right = columns - 1, top = 0, bottom = rows - 1;
        vector<int> order;
        //循环
        while(left <= right && top <= bottom){
            for(int column = left; column < right; column++){
                order.push_back(matrix[top][column]);
            }
            for(int row = top ; row <= bottom; row++){
                order.push_back(matrix[row][right]);
            }
            if(left < right && top < bottom){
                for(int column = right - 1; column >= left; column--){
                    order.push_back(matrix[bottom][column]);
                }
                for(int row = bottom - 1; row > top; row--){
                    order.push_back(matrix[row][left]);
                }
            }
            left++;
            top++;
            right--;
            bottom--;
        }
        return order;
    }
};