Leetcode: Spiral Matrix II

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最新推荐文章于 2025-05-16 12:14:55 发布

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本文介绍了一种生成指定大小的矩阵，元素按照螺旋顺序填充从1到n²的整数的方法。通过迭代n/2圈来构建矩阵，并在n为奇数时将n²填充至矩阵中心。

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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 ]
]

Iterate over n / 2 circles. If n is odd, add n^2 at the center of the matrix.

public class Solution {
    public int[][] generateMatrix(int n) {
        int[][] res = new int[n][n];
        int value = 1;
        for (int i = 0; i < n / 2; i++) {
            for (int j = i; j < n - 1 - i; j++) {
                res[i][j] = value++;
            }
            
            for (int j = i; j < n - 1 - i; j++) {
                res[j][n - 1 - i] = value++;
            }
            
            for (int j = n - 1 - i; j > i; j--) {
                res[n - 1 - i][j] = value++;
            }
            
            for (int j = n - 1 - i; j > i; j--) {
                res[j][i] = value++;
            }
        }
        
        if (n % 2 == 1) {
            res[n /2][n / 2] = value;
        }
        
        return res;
    }
}