leetcode刷题. 54. 螺旋矩阵

给定一个包含 m x n 个元素的矩阵（m 行, n 列），请按照顺时针螺旋顺序，返回矩阵中的所有元素。

 

    void recursion(vector<vector<int>> &matrix, int p1x, int p1y, int p2x, int p2y, vector<int> &output, int idx) {

        if(p1x > p2x || p1y > p2y)
            return;

        if(p1x == p2x) {
            for(int i = p1y; i <= p2y; i++)
                output[idx++] = matrix[p1x][i];
            return;
        }

        if(p1y == p2y) {
            for(int i = p1x; i <= p2x; i++)
                output[idx++] = matrix[i][p2y];
            return;
        }
        
        for(int i = p1y; i < p2y; i++)
            output[idx++] = matrix[p1x][i];
        
        for(int i = p1x; i < p2x; i++)
            output[idx++] = matrix[i][p2y];

        for(int i = p2y; i > p1y; i--)
            output[idx++] = matrix[p2x][i];

        for(int i = p2x; i > p1x; i--)
            output[idx++] = matrix[i][p1y];

        recursion(matrix, p1x + 1, p1y + 1, p2x - 1, p2y - 1, output, idx);
    }

    vector<int> spiralOrder(vector<vector<int>>& matrix) {

        if(matrix.empty())
            return {};
            
        int xlen = matrix.size();
        int ylen = matrix[0].size();
        vector<int> output(xlen * ylen , 0);
        recursion(matrix, 0, 0, xlen - 1, ylen - 1, output, 0);
        return output;
    }