Q29顺时针打印矩阵

顺时针打印矩阵

题目

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.

思路

对于行列分别为 r c 的矩阵

每次打印一圈

这一圈的起点是 (n, n), n 从0开始

用while循环包裹这个一圈，while循环的条件是：（r>2n, c>2n）

例如，要打印第二圈的话，n=1，矩阵必须满足，r>2 && c>2

每一圈打印的时候要注意停止标准！

特别注意：

1. 一圈只有1个元素
2. 一圈只有一行
3. 一圈只有一列

实现

class Solution {
public:
    vector<int> printMatrix(vector<vector<int> > matrix) {
        int rows = matrix.size();
        int columns = matrix.front().size();
        vector<int> out;
        int stR = 0, stC = 0;
        while(rows>stR*2 && columns>stC*2)
        {
            int r = stR, mr = stR;
            int c = stC, mc = stC;
            out.push_back(matrix[r][c]);
            while((++c)<(columns-stC))//右
            {
                out.push_back(matrix[r][c]);
                mc = c;
            }
            c = mc;
            while((++r)<(rows-stR))//下
            {
                out.push_back(matrix[r][c]);
                mr = r;
            }
            r = mr;
            while(mr>stR && ((--c)>=stC))//左
            {
                out.push_back(matrix[r][c]);
            }
            ++c;
            while(mc>stC && --r>stR)//上
            {
                out.push_back(matrix[r][c]);
            }
                
            ++stR;
            ++stC;
        }
        return out;
    }
};

//测试用例

#include <iostream>
#include <vector>
using namespace std;

void testClockWiseMtxPrint(int rows, int cols)
{
	cout << "start mtx generate and clock-wise print:" << endl;
	vector<vector<int>> mtx;
	int row = rows, col = cols;
	int k = 0;
	for (int i = 0; i < row; ++i)
	{
		vector<int> tmtx;
		for (int j = 0; j < col; ++j)
			tmtx.push_back(k++);
		mtx.push_back(tmtx);
	}
	cout << "MTX:" << endl;
	for (auto v : mtx)
	{
		for (auto e : v)
		{
			cout << e << " ";
		}
		cout << endl;
	}
	cout << "clock-wise MTX elements:" << endl;
	vector<int> numList = Solution().printMatrix(mtx);
	for (auto e : numList)
	{
		cout << e << " ";
	}
	cout << endl;
	cout << "---End-----" << endl;
}

void main()
{
	testClockWiseMtxPrint(1, 1);
	testClockWiseMtxPrint(1, 5);
	testClockWiseMtxPrint(4, 1);
	testClockWiseMtxPrint(5, 4);


	system("pause");
}