54. Spiral Matrix (Graph)

Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order.

For example,
Given the following matrix:

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

You should return [1,2,3,6,9,8,7,4,5].

思路：创建函数互相递归调用，函数的参数要包括方向

class Solution {
public:
    vector<int> spiralOrder(vector<vector<int>> &matrix) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        result.clear();
        if(matrix.empty()) return result;
        
        leftPos = 0; 
        rightPos = matrix[0].size()-1; 
        topPos = 0; 
        bottomPos = matrix.size()-1;
        goWider(matrix, true);
        return result;
    }
    void goWider(vector<vector<int>> &matrix, bool direct)
    {
        if(direct)
        {
            for(int i = leftPos; i<= rightPos; i++)
            {
                result.push_back(matrix[topPos][i]);
            }
            topPos++;
            if(topPos > bottomPos) return;
            goDeeper(matrix, true);
        }
        else
        {
            for(int i = rightPos; i>= leftPos; i--)
            {
                result.push_back(matrix[bottomPos][i]);
            }
            bottomPos--;
            if(topPos > bottomPos) return;
            goDeeper(matrix, false);
        }
    }
    void goDeeper(vector<vector<int>> &matrix, bool direct)
    {
        if(direct)
        {
            for(int i = topPos; i<= bottomPos; i++)
            {
                result.push_back(matrix[i][rightPos]);
            }
            rightPos--;
            if(leftPos > rightPos) return;
            goWider(matrix, false);
        }
        else
        {
            for(int i = bottomPos; i>= topPos; i--)
            {
                result.push_back(matrix[i][leftPos]);
            }
            leftPos++;
            if(leftPos > rightPos) return;
            goWider(matrix, true);
        }
    }
private:
    vector<int> result;
    int leftPos;
    int rightPos;
    int topPos;
    int bottomPos;
};