54. Spiral Matrix

54. Spiral Matrix 

Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order.

Example 1:

Input:
[
 [ 1, 2, 3 ],
 [ 4, 5, 6 ],
 [ 7, 8, 9 ]
]
Output: [1,2,3,6,9,8,7,4,5]
Example 2:

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

　　

python参考链接

 

 c++

class Solution {
public:
    vector<int> spiralOrder(vector<vector<int>>& matrix) {
        int m = matrix.size(), n = m ? matrix[0].size() : 0, u = 0, d = m - 1, l = 0, r = n - 1, p = 0;
        vector<int> order(m * n);
        while (u <= d && l <= r) {
            for (int col = l; col <= r; col++) {
                order[p++] = matrix[u][col];
            }
            if (++u > d) {
                break;
            }
            for (int row = u; row <= d; row++) {
                order[p++] = matrix[row][r];
            }
            if (--r < l) {
                break;
            }
            for (int col = r; col >= l; col--) {
                order[p++] = matrix[d][col];
            }
            if (--d < u) {
                break;
            }
            for (int row = d; row >= u; row--) {
                order[p++] = matrix[row][l];
            }
            if (l++ > r) {
                break;
            }
        }
        return order;
    }
};