剑指offer 面试题29 顺时针打印矩阵

题目描述
输入一个矩阵，按照从外向里以顺时针的顺序依次打印出每一个数字，例如，如果输入如下4 X 4矩阵： 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 则依次打印出数字1,2,3,4,8,12,16,15,14,13,9,5,6,7,11,10.

tips: 使用递归，注意处理只有一行，和只有一列的情况。

class Solution {
public:
    vector<int> printMatrix(vector<vector<int> > matrix) {
        vector<int> now;
        return recursivePrintMatrix(matrix,0,matrix.size()-1,0,matrix[0].size()-1,now);
    }
    vector<int> recursivePrintMatrix(vector<vector<int> >& matrix,int startX,int endX,int startY,int endY,vector<int> &resBefore) {
        if(startX>endX||startY>endY) {
            return resBefore;
        }
        vector<int> res=resBefore;
        // 只有一行
        if(startX==endX){
            for (int i = startY; i <= endY; i++) {
                res.push_back(matrix[startX][i]);
            }
            return res;
        }
        // 只有一列
        if(startY==endY){
            for (int i = startX; i <= endX; i++) {   
                res.push_back(matrix[i][endY]);
            }
            return res;
        }
        for (int i = startY; i < endY; i++)
        {
            res.push_back(matrix[startX][i]);
        }
        for (int i = startX; i < endX; i++)
        {   
            res.push_back(matrix[i][endY]);
        }

        for (int i = endY; i >startY; i--)
        {
            res.push_back(matrix[endX][i]);
        }
        for (int i = endX; i >startX; i--)
        {
            res.push_back(matrix[i][startX]);
        }
        return recursivePrintMatrix(matrix,startX+1,endX-1,startY+1,endY-1,res);
    }
};