leetcode:Spiral Matrix II

最新推荐文章于 2021-12-10 15:40:33 发布

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本文介绍了一个算法，该算法接收一个整数 n，并生成一个 n x n 的矩阵，矩阵中的元素从1到n²，按螺旋顺序填充。文章通过示例说明了当 n 为3时所返回的具体矩阵形式，并提供了 C++ 代码实现。

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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 ]
]

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class Solution {
public:
vector<vector<int> > generateMatrix(int n) {
    
    vector<vector<int> >  retVtr(n, vector<int>(n));
    
    if (n == 0)
    {
        return retVtr;
    }
    
    int offset = 0;

    int N = n*n;
    int curVal = 1;
    while (curVal <= N)
    {
        if (curVal == N)
        {
            retVtr[offset][offset] = curVal;
            break;
        }
        
        for (int idx=offset; idx<n-1-offset && curVal<=N; idx++)
            retVtr[offset][idx] = curVal++;
        
        for (int idx=offset; idx<n-1-offset && curVal<=N; idx++)
            retVtr[idx][n-1-offset] = curVal++;
        
        for (int idx=n-1-offset; idx>offset && curVal<=N; idx--)
            retVtr[n-1-offset][idx] = curVal++;
        
        for (int idx=n-1-offset; idx>offset && curVal<=N; idx--)
            retVtr[idx][offset] = curVal++;
        
        offset++;
    }
    
    return retVtr;
}
};