const climbingStairs = N => {
let count = 0
const dfs = depth => {
if (depth === N) {
count += 1
return
}
if (depth > N) {
return
}
dfs(depth + 1)
dfs(depth + 2)
}
dfs(0)
return count
}
test('climbingStairs', () => {
expect(climbingStairs(7)).toBe(21)
})