Spiral Matrix
描述
Given a matrix of m × 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].
分析
模拟。
解法1 迭代
// LeetCode, Spiral Matrix
// @author 龚陆安 (http://weibo.com/luangong)
// 时间复杂度O(n^2)，空间复杂度O(1)
class Solution {
public:
vector<int> spiralOrder(vector<vector<int> >& matrix) {
vector<int> result;
if (matrix.empty()) return result;
int beginX = 0, endX = matrix[0].size() - 1;
int beginY = 0, endY = matrix.size() - 1;
while (true) {
// From left to right
for (int j = beginX; j <= endX; ++j) result.push_back(matrix[beginY][j]);
if (++beginY > endY) break;
// From top to bottom
for (int i = beginY; i <= endY; ++i) result.push_back(matrix[i][endX]);
if (beginX > --endX) break;
// From right to left
for (int j = endX; j >= beginX; --j) result.push_back(matrix[endY][j]);
if (beginY > --endY) break;
// From bottom to top
for (int i = endY; i >= beginY; --i) result.push_back(matrix[i][beginX]);
if (++beginX > endX) break;
}
return result;
}
};