Algorithm questions daily practice---Day 65: Spiral Matrix II

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1. Problem description

Given a positive integer  n , generate a   square matrix  containing 1 all  n2 elements in a spiral arranged in clockwise order   .n x nmatrix

Topic link: Spiral Matrix II .

Second, the subject requirements

Example 1

输入： n = 3
输出： [[1,2,3],[8,9,4],[7,6,5]]
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Example 2

输入： n = 1
输出： [[1]]
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1.模拟计算
2.建议用时15~35min
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3. Problem Analysis

This question is essentially the same as the Algorithm Question Daily Practice --- Day 64: Spiral Matrix I.

It's just the first question that gives you the array and lets you output. The second question gives you ranges and lets you output arrays. It is recommended that you do the 螺旋矩阵 Iquestion (the explanation is more detailed), and then come back and do this question to consolidate the relevant knowledge.

Fourth, the encoding implementation

class Solution {
public:
    vector<vector<int>> generateMatrix(int n) {
        int k=1,i,u=0,d=n-1,l=0,r=n-1;//初始化数据，定义上下左右四个方向范围
        vector<vector<int>>v(n, vector<int>(n));//定义二维数组
        while(1)//循环判断
        {
            for(i=l;i<=r;i++) v[u][i]=k++;//l->r方向
            if(++u>d) break;
            for(i=u;i<=d;i++) v[i][r]=k++;//u->d方向
            if(--r<l) break;
            for(i=r;i>=l;i--) v[d][i]=k++;//r->方向
            if(--d<u) break;
            for(i=d;i>=u;i--) v[i][l]=k++;//d->u方向
            if(++l>r) break;
        }
        return v;

    }
};
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5. Test results