54. Spiral Matrix

題目

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]. 

解析

• 自己親自寫才知道很多細節問題：
• bug1:y0==y1寫成y0=y1賦值語句
• bug2: for (int row = x1 - 1; row > x0;row--)
  小標越界row=x1+1
• bug3: 輸入為空矩陣判斷if ( matrix.empty())後面判斷row<=0||col<=0此時已經出現問題了

class Solution_54 {
public:
    void help(vector<vector<int>>& matrix,vector<int> &res, int x0, int y0, int x1, int y1)
    {
        if (x0==x1&&y0==y1)
        {
            res.push_back(matrix[x0][y0]);
        }else
 
 if (x0==x1) //最後一行
        {
            for (int i = y0; i <= y1;i++)
            {
                res.push_back(matrix[x0][i]);
            }
        }else if (y1==y0)
        {
            for (int i = x0; i <= x1;i++)
            {
                res.push_back(matrix[i][y0]);
            }
        }
        else
 

        {
            for (int col = y0; col <= y1;col++) 
            {
                res.push_back(matrix[x0][col]);
            }
            for (int row = x0 + 1; row <= x1;row++)
            {
                res.push_back(matrix[row][y1]);
            }
            for (int col = y1 - 1; col >= y0;col--)
            {
                res.push_back(matrix[x1][col]);
            }
            for (int row = x1 - 1; row > x0;row--)
            {
                res.push_back(matrix[row][y0]);
            }
        }
        return;
    }

    vector<int> spiralOrder(vector<vector<int>>& matrix) {
        vector<int> res;
        if ( matrix.empty()) //
        {
            return vector<int>(); //res;
        }
        int row = matrix.size();
        int col = matrix[0].size(); //後面判斷錯誤：row <= 0 || col <= 0 ，需要計算row,col調用size()出錯，需要在函數開始判斷

        int x0 = 0, y0 = 0, x1 = row - 1, y1 = col - 1;
        while (x0<=x1&&y0<=y1)
        {
            help(matrix,res, x0, y0, x1, y1);
            x0++;
            y0++;
            x1--;
            y1--;
        }

        return res;
    }
};

題目來源

• 矩陣的操作
• 54. Spiral Matrix

54. Spiral Matrix