leetcode 59. Spiral Matrix II 螺旋方式写矩阵

﹏ヽ暗。殇╰゛Y 2022-06-09 10:55 205阅读 0赞

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:  
\[  
\[ 1, 2, 3 \],  
\[ 8, 9, 4 \],  
\[ 7, 6, 5 \]  
\]

和上一道题[leetcode 54. Spiral Matrix 螺旋方式读取矩阵][leetcode 54. Spiral Matrix]相反的是，本题要求的是按照螺旋的方式写矩阵，实现方法一模一样。

代码如下：

public class Solution
    {
        public int[][] generateMatrix(int n) 
        {
            if(n==0)
                return new int[0][0];
    
            int [][]matrix=new int[n][n];
            int count=1;
            int top=0,bottom=matrix.length-1;
            int left=0,right=matrix[0].length-1;
            while(true)
            {
                for(int i=left;i<=right;i++)
                    matrix[top][i]=count++;
                top++;
                if(top>bottom)
                    break;
    
                for(int i=top;i<=bottom;i++)
                    matrix[i][right]=count++;
                right--;
                if(left>right)
                    break;
    
                for(int i=right;i>=left;i--)
                    matrix[bottom][i]=count++;
                bottom--;
                if(top>bottom)
                    break;
    
                for(int i=bottom;i>=top;i--)
                    matrix[i][left]=count++;
                left++;
                if(left>right)
                    break;  
            }   
            return matrix;
        }
    }

下面是C++的做法，这个和上一道题螺旋方式读取矩阵的做法一模一样

代码如下：

#include <iostream>
    #include <vector>
    #include <map>
    #include <unordered_map>
    #include <set>
    #include <unordered_set>
    #include <queue>
    #include <stack>
    #include <string>
    #include <climits>
    #include <algorithm>
    #include <sstream>
    #include <functional>
    #include <bitset>
    #include <numeric>
    #include <cmath>
    #include <regex>
    
    using namespace std;
    
    
    class Solution
    {
    public:
        vector<vector<int>> generateMatrix(int n)
        {
            vector<vector<int>> mat(n,vector<int>(n,0));
            if (n <= 0)
                return mat;
    
            int count = 1 , left = 0, right = mat[0].size() - 1;
            int up = 0, down = mat.size() - 1;
            while (true)
            {
                for (int i = left; i <= right; i++)
                    mat[up][i] = count++;
                up++;
                if (up > down)
                    break;
    
                for (int i = up; i <= down; i++)
                    mat[i][right] = count++;
                right--;
                if (left > right)
                    break;
    
                for (int i = right; i >= left; i--)
                    mat[down][i] = count++;
                down--;
                if (up > down)
                    break;
    
                for (int i = down; i >= up; i--)
                    mat[i][left] = count++;
                left++;
                if (left > right)
                    break;
            }
            return mat;
        }
    };

[leetcode 54. Spiral Matrix]: http://blog.csdn.net/jackzhang_123/article/details/77837040