[swift] LeetCode 70. Climbing Stairs

You are climbing a stair case. It takes n steps to reach to the top.

Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?

func climbStairs(_ n: Int) -> Int {
    if n < 4 { return n }
    var arr = Array(repeating: 1, count: n+1)

    arr[2] = 2; arr[3] = 3
    for i in (4...n) {
        arr[i] = arr[i-1] + arr[i-2]
    }

    return arr[n]
}

func climbStairs(_ n: Int) -> Int {

if n < 4 { return n }

var arr = Array(repeating: 1, count: n+1)

arr[2] = 2; arr[3] = 3

for i in (4...n) {

arr[i] = arr[i-1] + arr[i-2]

}

return arr[n]

}

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