leetcode — spiral-matrix-ii

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

/**
* Source : https://oj.leetcode.com/problems/spiral-matrix-ii/ *
* Created by lverpeng on 2017/7/19.
*
* 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 SpiralMatrix2 {

public List<Integer[]> build (int n) {
List<Integer[]> result = new ArrayList<Integer[]>();
for (int i = 0; i < n; i++) {
result.add(new Integer
);
}
int row = 0;
int col = 0;
int count = 1;
for (; col < (n+1) / 2 && row < (n+1) / 2; row ++, col++) {
for (int i = col; i < n - col; i++) {
result.get(row)[i] = count++;
}
for (int i = row + 1; i < n - row; i ++) {
result.get(i)[n - col - 1] = count++;
}
for (int i = n - col - 2; i >= col; i--) {
result.get(n - row - 1)[i] = count++;
}
for (int i = n - row - 2; i > row; i--) {
result.get(i)[col] = count++;
}
}
return result;
}

public static void print (List<Integer[]> list) {
for (Integer[] arr : list) {
System.out.println(Arrays.toString(arr));
}
System.out.println();
}

public static void main(String[] args) {

SpiralMatrix2 spiralMatrix2 = new SpiralMatrix2();
print(spiralMatrix2.build(0));
print(spiralMatrix2.build(1));
print(spiralMatrix2.build(2));
print(spiralMatrix2.build(3));
print(spiralMatrix2.build(4));
print(spiralMatrix2.build(5));
}

}