[leetcode] 54. Spiral Matrix 解题报告

题目链接：https://leetcode.com/problems/spiral-matrix/

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：设置两个表示行进方向的向量flagX，flagY，还有边界值，然后在其到达边界的时候改变向量的值。每次位置累加为( x+flagX, y+flagY)。

大学的时候碰到过这个题，感觉挺麻烦的，现在做了感觉还是挺简单的。

代码如下：

class Solution {
public:
    vector<int> spiralOrder(vector<vector<int>>& matrix) {
        if(matrix.size() == 0) return result;
        int flagX = 1, flagY = 0, i =0, x = 0, y =0;
        int left = 0, right = matrix[0].size()-1, top = 0, bottom = matrix.size()-1;
        int cnt = matrix.size()* matrix[0].size();
        
        while(i < cnt)
        {
            result.push_back(matrix[y][x]);
            if(x >= right && flagX == 1)//遇到右边界
            {
                flagX = 0;
                flagY = 1;
                top++;
            }
            else if(y >= bottom && flagY == 1)//遇到下边界
            {
                flagX = -1;
                flagY = 0;
                right--;
            }
            else if(x <= left && flagX == -1)//遇到左边界
            {
                flagX = 0;
                flagY = -1;
                bottom--;
            }
            else if(y <= top && flagY == -1)//遇到上边界
            {
                flagX = 1;
                flagY = 0;
                left++;
            }
            
            x += flagX;
            y += flagY;
            i++;
        }
        return result;
    }
private:
    vector<int> result;
};