59. 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 ]
]

和spiral matrix1很像，代码如下：

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public class Solution {

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

int[][] res=  new int[n][n];

if(n==0) return res;

if(n==1){

res[0][0] = 1;

return res;

}

int rowbegin = 0;

int rowend = n-1;

int colbegin = 0;

int colend = n-1;

int num = 1;

while(true){

for(int i=colbegin;i<=colend;i++){

res[rowbegin][i] = num++;

}

rowbegin++;

if(rowbegin>rowend) break;

for(int i=rowbegin;i<=rowend;i++){

res[i][colend] = num++;

}

colend--;

if(colbegin>colend) break;

for(int i=colend;i>=colbegin;i--){

res[rowend][i] = num++;

}

rowend--;

if(rowbegin>rowend) break;

for(int i=rowend;i>=rowbegin;i--){

res[i][colbegin] = num++;

}

colbegin++;

if(colbegin>colend) break;

}

return res;

}

}