Title
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 ]
]
Solution
//cpp:
class Solution {
public:
vector<vector<int>> generateMatrix(int n) {
int c1 = 0, c2 = n-1;
int r1 = 0, r2 = n-1;
int x = 1;
vector<vector<int>> v;
v.resize(n);
for (int i = 0; i<n; i++)
v[i].resize(n);
while (c1 <= c2 && r1 <= r2) {
for (int i = c1; i <= c2; i++) {
v[r1][i] = x++;
}
for (int i = r1 + 1; i<r2; i++) {
v[i][c2] = x++;
}
if (c1<c2&&r1 <= r2) {
for (int i = c2; i >= c1; i--) {
v[r2][i] = x++;
}
for (int i = r2 - 1; i>r1; i--) {
v[i][c1] = x++;
}
}
c1++;
c2--;
r1++;
r2--;
}
return v;
}
};