Given a positive integer n, generate a square matrix filled with elements from 1 to n2 in spiral order.
Example:
Input: 3 Output: [ [ 1, 2, 3 ], [ 8, 9, 4 ], [ 7, 6, 5 ] ]
Tip: The same is divided into four steps, and the rows and columns are represented by i j and its deformation and exchange position.
Answer:
class Solution {
public:
vector<vector<int> > generateMatrix(int n) {
vector<vector<int> > ret( n, vector<int>(n) );
int k = 1, i = 0;
while( k <= n * n )
{
int j = i;
// four steps
while( j < n - i ) // 1. horizonal, left to right
ret [i] [j ++] = k ++;
j = i + 1;
while( j < n - i ) // 2. vertical, top to bottom
ret [j ++] [ni-1] = k ++;
j = n - i - 2;
while( j > i ) // 3. horizonal, right to left
ret [ni-1] [j--] = k ++;
j = n - i - 1;
while( j > i ) // 4. vertical, bottom to top
ret [j -] [i] = k ++;
i++; // next loop
}
return ret;
}
};