Spiral Matrix II

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 ]

]

C++实现代码：（注意奇数和偶数的不同）

#include<iostream>

#include<vector>

using namespace std;



class Solution

{

public:

    vector<vector<int> > generateMatrix(int n)

    {

        if(n==0)

            return vector<vector<int> >();

        vector<vector<int> > vec(n,vector<int>(n));

        int i,j;

        int count=1;

        i=0,j=0;

        while(((n%2)&&(count<n*n))||((n%2==0)&&(count<=n*n)))

        {

            for(; j<n-i-1; j++)

            {

                vec[i][j]=count;

                count++;

            }

            for(; i<j; i++)

            {

                vec[i][j]=count;

                count++;

            }

            for(; j>n-i-1; j--)

            {

                vec[i][j]=count;

                count++;

            }

            for(; i>j; i--)

            {

                vec[i][j]=count;

                count++;

            }

            i++;

            j++;

        }

        if(n%2)

            vec[i][j]=count;

        return vec;

    }

};



int main()

{

    Solution s;

    vector<vector<int> > result=s.generateMatrix(4);

    for(auto a:result)

    {

        for(auto v:a)

            cout<<v<<" ";

        cout<<endl;

    }

    cout<<endl;

}

 改进的方法，与Spiral Matrix类似的方法：

class Solution {

public:

    vector<vector<int> > generateMatrix(int n) {

        if(n<=0)

            return vector<vector<int> >();

        int count=1;

        int xmin=0;

        int xmax=n-1;

        int ymin=0;

        int ymax=n-1;

        vector<vector<int> > res(n,vector<int>(n));

        int i=0;

        int j=0;

        res[i][j]=count++;

        while(count<=n*n)

        {

            while(j<xmax) res[i][++j]=count++;

            if(++ymin>ymax)

                break;

            while(i<ymax) res[++i][j]=count++;

            if(--xmax<xmin)

                break;

            while(j>xmin) res[i][--j]=count++;

            if(--ymax<ymin)

                break;

            while(i>ymin) res[--i][j]=count++;

            if(++xmin>xmax)

                break;

        }

        return res;

    }

};