leetcode59 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 ]
]

class Solution {
public:
vector<vector<int>> generateMatrix(int n) {
vector<vector<int> > ans;

if(n<=0)
return ans;

vector<int> temp(n,0);
for(int i=0;i<n;i++)
{
ans.push_back(temp);
}

int xmin=0,ymin=0,xmax=n-1,ymax=n-1;

int total=n*n;

ans[0][0]=1;
int dir=1;
int x=0,y=0;
int count=1;

while(count<total)
{
if(dir==1)
{
if(y+1>ymax)
{
xmin++;
dir=2;
}
else
{
y++;
count++;
ans[x][y]=count;
}
}
else if(dir==2)
{
if(x+1>xmax)
{
ymax--;
dir=3;
}
else
{
x++;
count++;
ans[x][y]=count;
}
}
else if(dir==3)
{
if(y-1<ymin)
{
xmax--;
dir=4;
}
else
{
y--;
count++;
ans[x][y]=count;
}
}
else
{
if(x-1<xmin)
{
ymin++;
dir=1;
}
else
{
x--;
count++;
ans[x][y]=count;
}
}
}
return ans;
}
};

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