LeetCode 54.Spiral Matrix (螺旋矩阵)-蒲公英云

LeetCode 54.Spiral Matrix (螺旋矩阵)

题目描述：

给定一个包含 m x n 个元素的矩阵（m 行, n 列），请按照顺时针螺旋顺序，返回矩阵中的所有元素。

示例 1:

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

示例 2:

输入:
[
  [1, 2, 3, 4],
  [5, 6, 7, 8],
  [9,10,11,12]
]
输出: [1,2,3,4,8,12,11,10,9,5,6,7]

AC C++ Solution:

class Solution {
public:
    vector<int> spiralOrder(vector<vector<int>>& matrix) {
        vector<int> res;
        if(matrix.size() == 0) {
            return res;
        }
        int rowBegin = 0;
        int rowEnd = matrix.size()-1;
        int colBegin =  0;
        int colEnd = matrix[0].size()-1;
        while(rowBegin <= rowEnd && colBegin <= colEnd) {
            //向右遍历
            for (int i = colBegin; i <= colEnd; i++)
                res.push_back(matrix[rowBegin][i]);
            rowBegin++;
            //向下遍历
            for (int i = rowBegin; i <= rowEnd; i++)
                res.push_back(matrix[i][colEnd]);
            colEnd--;
            //向左遍历
            if(rowBegin <= rowEnd) {
                for(int i = colEnd; i >= colBegin; i--)
                    res.push_back(matrix[rowEnd][i]);
            }
            rowEnd--;
            //向上遍历
            if(colBegin <= colEnd) {
                for(int i = rowEnd; i >= rowBegin; i--)
                    res.push_back(matrix[i][colBegin]);
            }
            colBegin++;
        }
        return res;
    }
};