【leetcode】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 ]

]
public class Solution {
public int[][] generateMatrix(int n) {
int[][] matrix = new int

;
if (n == 0){
return matrix;
}
int rowBegin = 0;
int rowEnd = n-1;
int colBegin = 0;
int colEnd = n-1;
int num = 1;
while (rowBegin <= rowEnd && colBegin <= colEnd){
for (int j = colBegin; j <= colEnd; j++){
matrix[rowBegin][j] = num++;
}
rowBegin++;
for (int j = rowBegin; j <= rowEnd; j++){
matrix[j][colEnd] = num++;
}
colEnd--;

//对于n*n矩阵此处的if判断可去掉
if (rowBegin <= rowEnd){
for (int j = colEnd; j >= colBegin; j--){
matrix[rowEnd][j] = num++;
}
}
rowEnd--;
if (colBegin <= colEnd){
for (int j = rowEnd; j >= rowBegin; j--){
matrix[j][colBegin] = num++;
}
}
colBegin++;
}
return matrix;
}
}