LeetCode Spiral Matrix II

class Solution {

    public:

            vector<vector<int> > generateMatrix(int n) {

                vector<vector<int> > matrix;

                if (n < 1) return matrix;



                for (int i=0; i<n; i++) {

                    matrix.push_back(vector<int>(n, 0));

                }

                int left = 0, top = 0, right = n - 1, bottom = n - 1;

                int last = 1;

                while (left <= right && top <= bottom) {

                    last = circle_walk(last, left, top, right, bottom, matrix);

                    left++, top++, bottom--, right--;

                }

                return matrix;

            }



            int circle_walk(int start, int left, int top, int right, int bottom, vector<vector<int> >& map) {

                    int rows = 0;

                    if (map.size() < 1 || map[0].size() < 1) return start;

                            

                    // top row

                    for (int i=left; i<=right; i++) {

                        map[top][i] = start++;

                    }



                    // right col

                    for (int i=top+1; i<=bottom; i++) {

                       map[i][right] = start++;

                    }

                    

                    // bottom row

                    for (int i=right-1; bottom != top && i>=left; i--) {

                        map[bottom][i] = start++;

                    }



                    // left col

                    for (int i=bottom-1; left != right && i>top; i--) {

                        map[i][left] = start++;

                    }

                    return start;

            }

};

再水一发

第二轮：

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 ]

]

 1 class Solution {

 2 public:

 3     vector<vector<int> > generateMatrix(int n) {

 4         vector<vector<int> > matrix(n, vector<int>(n, 0));

 5         

 6         if (n < 1) {

 7             return matrix;

 8         }

 9         

10         int xn = n;

11         int yn = n;

12         

13         int col = -1;

14         int row = 0;

15         

16         int seq = 1;

17         

18         while (true) {

19             for (int i=0; i<xn; i++) matrix[row][++col] = seq++;        

20             if (--yn == 0) break;

21             

22             for (int i=0; i<yn; i++) matrix[++row][col] = seq++;

23             if (--xn == 0) break;

24             

25             for (int i=0; i<xn; i++) matrix[row][--col] = seq++;

26             if (--yn == 0) break;

27             

28             for (int i=0; i<yn; i++) matrix[--row][col] = seq++;

29             if (--xn == 0) break;

30         }

31         

32         return matrix;

33     }

34 };