Spiral Matrix 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 ]

]

 [ 1, 2, 3 ],

 [ 8, 9, 4 ],

 [ 7, 6, 5 ]
以这种方式进行循环即可。

 1 public class Solution {

 2     public int[][] generateMatrix(int n) {

 3         // Note: The Solution object is instantiated only once and is reused by each test case.

 4         int[][] result = new int[n][n];

 5         int a = 1;

 6         int top = 0;

 7         int bot = n - 1;

 8         int left = 0;

 9         int right = n - 1;

10         while(top < bot && left < right){

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

12             {

13                 result[top][i] = a ++;

14             }

15             for(int i = top; i < bot; i ++)

16             {

17                 result[i][right] = a ++;

18             }

19             for(int i = right; i > left; i --)

20             {

21                 result[bot][i] = a ++;

22             }

23             for(int i = bot; i > top; i --)

24             {

25                 result[i][left] = a ++;    

26             }

27             top ++;

28             bot --;

29             left ++;

30             right --;

31         }

32         if(top == bot && left == right){//对于n 为奇数的情况。

33             result[top][left] = a;

34         }

35         return result;

36     }

37 }

 第三遍：

 1 public class Solution {

 2     public int[][] generateMatrix(int n) {

 3         int[][] result = new int[n][n];

 4         if(n == 0) return result;

 5         int top = 0, bot = n - 1, num = 1;

 6         while(top < bot){

 7             for(int i = top; i < bot; i ++)

 8                 result[top][i] = num ++;

 9             for(int i = top; i < bot; i ++)

10                 result[i][bot] = num ++;

11             for(int i = bot; i > top; i --)

12                 result[bot][i] = num ++;

13             for(int i = bot; i > top; i --)

14                 result[i][top] = num ++;

15             top ++; bot --;

16         }

17         if(top == bot) result[top][bot] = num;

18         return result;

19     }

20 }