LeetCode54 Spiral Matrix

题目：

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]. （Medium）

分析：

题目没有什么复杂的算法要应用，就是一行一列输出，处理好细节即可。

比较清晰的写法是搞一个rowBegin, rowEnd, colBegin, colEnd， 并在处理完一行/一列后更新值，并判断是否仍然满足 rowBegin <= rowEnd && colBegin <= colEnd

代码：

 class Solution {
 public:
     vector<int> spiralOrder(vector<vector<int>>& matrix) {
         vector<int> result;
         if (matrix.size() == ) {
             return result;
         }
         int m = matrix.size(), n = matrix[].size();
         int rowBegin = , rowEnd = m - , colBegin = , colEnd = n - ;
         while (rowBegin <= rowEnd && colBegin <= colEnd) {
             for (int i = colBegin; i <= colEnd; ++i ) {
                 result.push_back(matrix[rowBegin][i]);
             }
             rowBegin++;
             if (rowBegin > rowEnd) {
                 break;
             }
             for (int i = rowBegin; i <= rowEnd; ++i) {
                 result.push_back(matrix[i][colEnd]);
             }
             colEnd--;
             if (colBegin > colEnd) {
                 break;
             }
             for (int i = colEnd; i >= colBegin; --i) {
                 result.push_back(matrix[rowEnd][i]);
             }
             rowEnd--;
             if (rowBegin > rowEnd) {
                 break;
             }
             for (int i = rowEnd; i>= rowBegin; --i) {
                 result.push_back(matrix[i][colBegin]);
             }
             colBegin++;
         }
         return result;
     }
 };