Total the two diagonals
A scoring sheet is a square grid, and the bonus is whatever sits on the two diagonals.
- The grid is square.
- Add every cell on the top-left to bottom-right diagonal, and every cell on the other one.
- On an odd-sized grid the centre belongs to both diagonals, and is counted once.
- An empty grid totals zero.
diagonalTotal(sheet: list<list<int>>) → int
Go needs a compiler and Drill does not host one yet, so this page is the reference rather than an exercise: the problem, worked examples, and the solution in full. To type it out, the same problem runs in Python.
Where you start
func diagonalTotal(sheet [][]int) int {
}Worked examples
| Call | Result |
|---|---|
diagonalTotal([][]int{[]int{1, 2, 3}, []int{4, 5, 6}, []int{7, 8, 9}}) | 25 |
diagonalTotal([][]int{[]int{1, 2}, []int{3, 4}}) | 10 |
diagonalTotal([][]int{[]int{5}}) | 5 |
diagonalTotal([][]int{}) | 0 |
Hint
Walk one index down the grid. At row i the two diagonal cells are column i and column (last - i) — and on an odd grid those meet in the middle.
Reference solution in Go
func diagonalTotal(sheet [][]int) int {
total := 0
n := len(sheet)
for i := 0; i < n; i++ {
total += sheet[i][i]
if i != n-1-i {
total += sheet[i][n-1-i]
}
}
return total
}