Spiral Matrix I, II

I. 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].

Analyse: four steps. Top right, right down, bottom left, left up.

Runtime: 0ms.

 1 class Solution {
 2 public:
 3     vector<int> spiralOrder(vector<vector<int>>& matrix) {
 4         int m = matrix.size();
 5         vector<int> result;
 6         if(m == 0) return result;
 7         
 8         int n = matrix[0].size();
 9         int x = 0, y = 0;
10         while(m > 0 && n > 0){
11             if(m == 1){
12                 for(int i = 0; i < n; i++)
13                     result.push_back(matrix[x][y++]);
14                 break;
15             }
16             else if(n == 1){
17                 for(int j = 0; j < m; j++)
18                     result.push_back(matrix[x++][y]);
19                 break;
20             }
21             
22             for(int i = 0; i < n - 1; i++){//top-right scan
23                 result.push_back(matrix[x][y++]);
24             }
25             for(int i = 0; i < m - 1; i++){//right-down scan
26                 result.push_back(matrix[x++][y]);
27             }
28             for(int i = 0; i < n - 1; i++){//bottom-left scan
29                 result.push_back(matrix[x][y--]);
30             }
31             for(int i = 0; i < m - 1; i++){//left-up scan
32                 result.push_back(matrix[x--][y]);
33             }
34             
35             x++;
36             y++;
37             m -= 2;
38             n -= 2;
39         }
40         return result;
41     }
42 };

II. Given an integer n, generate a square matrix filled with elements from 1 to n2 in spiral order.

For example,
Given n = 3,

You should return the following matrix:

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

Analyse: The same as 1.

Runtime: 8ms.

 1 class Solution {
 2 public:
 3     vector<vector<int>> generateMatrix(int n) {
 4         vector<vector<int> > result(n, vector<int>(n, 0));
 5         if(n == 0) return result;
 6         if(n == 1){
 7             result[0][0] = 1;
 8             return result;
 9         }
10         
11         int current = 0;
12         int x = 0, y = 0;
13         int row = n, col = n;
14         while(row > 0 && col > 0){
15             if(row == 1){
16                 for(int i = 0; i < col; i++)
17                     result[x][y++] = ++current;
18                 break;
19             }
20             else if(col == 1){
21                 for(int i = 0; i < row; i++)
22                     result[x++][y] = ++current;
23                 break;
24             }
25             
26             for(int i = 0; i < col - 1; i++){//put top-right
27                 result[x][y++] = ++current;
28             }
29             for(int i = 0; i < row - 1; i++){//put top-down
30                 result[x++][y] = ++current;
31             }
32             for(int i = 0; i < col - 1; i++){//put bottom-left
33                 result[x][y--] = ++current;
34             }
35             for(int i = 0; i < row - 1; i++){//put bottom-up
36                 result[x--][y] = ++current;
37             }
38             x++;
39             y++;
40             row -= 2;
41             col -= 2;
42         }
43         return result;
44     }
45 };