LeetCode——Spiral Matrix II

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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 ]]

原题链接：https://oj.leetcode.com/problems/spiral-matrix-ii/

之前的一题是将螺旋结构的二维数组转成一维数组，此题正好相反，故只需将原来的位置上取下来的元素放回去。

public class SpiralMatrixII {public static void main(String[] args) {int[][] matrix = new SpiralMatrixII().generateMatrix(3);for(int[] r : matrix){for(int c : r)System.out.print(c + "\t");System.out.println();}}public int[][] generateMatrix(int n) {int[][] matrix = new int[n][n];if(n == 0)return matrix;int l = 0, r = matrix[0].length - 1;int u = 0, d = matrix.length - 1;int num = 1;while (l <= r && u <= d) {for (int i = l; i <= r; i++)matrix[u][i] = num++;u++;if (u > d)continue;for (int i = u; i <= d; i++)matrix[i][r] = num++;r--;if (l > r)continue;for (int i = r; i >= l; i--)matrix[d][i] = num++;d--;if (u > d)continue;for (int i = d; i >= u; i--)matrix[i][l] = num++;l++;}return matrix;}}

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