Title Description

Give you a positive integer n , Generate a include 1 To n² All the elements , And the elements are arranged in a clockwise spiral order n x n square matrix matrix .
Example 1：

 Input ：n = 3
 Output ：[[1,2,3],[8,9,4],[7,6,5]]

Ideas

The idea of this problem is the same as that I wrote before Spiral matrix They have the same idea of solving problems , The reader can read it directly Spiral matrix How to solve the problem . The former is applicable to any matrix ( The number of rows and columns can not be equal ), This requires a square matrix ( The number of columns is equal ), It belongs to the special case of the former .

vector<vector<int>> generateMatrix(int n){
    
	vector<vector<int>> ans(n,vector<int>(n,0));
	int up=0,left=0,down=n-1,right=n-1;
	int count=1;// Used to count 
	while(true){
    
		
		// Left to right 
		for(int i=left;i<=right;i++)
			ans[up][i]=count++;
		if(++up > down)
			break;
		
		// Up and down 
		for(int i=up;i<=down;i++)
			ans[i][right]=count++;
		if(--right < left)
			break;
		
		// Right to left 
		for(int i=right;i>=left;i--)
			ans[down][i]=count++;
		if(--down < up)
			break;
		
		// Down to up 
		for(int i=down;i>=up;i--)
			ans[i][left]=count++;
		if(++left > right)
			break;
	}
	return ans;
}