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/*

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[][] geneareteMatrix(int n) {

if (n < 1) return null;

int[][] matrix = new int[n][n];

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

int x = 0, y = 0, val = 1;

while (true) {

if (matrix[x][y] != 0) break;

if (x == top && y != right) {

matrix[x][y++] = val++;

} else if (x != bottom && y == right) {

matrix[x++][y] = val++;

} else if (x == bottom && y != left) {

matrix[x][y--] = val++;

} else if (x != top+1 && y == left) {

matrix[x--][y] = val++;

}else if (x == top+1 && y == left) {

left++;

right--;

top++;

bottom--;

}

}

return matrix;

}

}