2579: Count-Total-Number-of-Colored-Cells
Medium
You can calculate the number of coloured cells in
n cells instantly by realising that:
Therefore, you can simply just return
2 * (n-1)^2 + (2n - 1).
Code:
class Solution {
public:
long long coloredCells(int n) {
return 2 * ((long long) (n-1) * (n-1)) + (n * 2 - 1);
}
};