59. 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 ]
]

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class Solution {
public:
void fillvec(vector<vector<int>>& v1,int start,int len,int &num)
{
int i=0,j=0;
while(j<len)
{
v1[start+i][j+start]=num++;
j++;
}
j-=1;
i+=1;
while(i<len)
{
v1[start+i][j+start]=num++;
i++;
}
i-=1;
j-=1;
while(j>=0)
{
v1[start+i][j+start]=num++;
j--;
}
j+=1;
i-=1;
while(i>0)
{
v1[start+i][j+start]=num++;
i--;
}
return ;
}
vector<vector<int>> generateMatrix(int n) {
vector<vector<int>> v1(n,vector<int>(n,0));
int j=0;
int num=1;
for(int i=0;i<n;i+=2)
fillvec(v1,j++,n-i,num);
return v1;
}
};