50 lines
1.2 KiB
Swift
50 lines
1.2 KiB
Swift
/**
|
|
* File: climbing_stairs_dp.swift
|
|
* Created Time: 2023-07-15
|
|
* Author: nuomi1 (nuomi1@qq.com)
|
|
*/
|
|
|
|
/* Climbing stairs: Dynamic programming */
|
|
func climbingStairsDP(n: Int) -> Int {
|
|
if n == 1 || n == 2 {
|
|
return n
|
|
}
|
|
// Initialize dp table, used to store subproblem solutions
|
|
var dp = Array(repeating: 0, count: n + 1)
|
|
// Initial state: preset the smallest subproblem solution
|
|
dp[1] = 1
|
|
dp[2] = 2
|
|
// State transition: gradually solve larger subproblems from smaller ones
|
|
for i in 3 ... n {
|
|
dp[i] = dp[i - 1] + dp[i - 2]
|
|
}
|
|
return dp[n]
|
|
}
|
|
|
|
/* Climbing stairs: Space-optimized dynamic programming */
|
|
func climbingStairsDPComp(n: Int) -> Int {
|
|
if n == 1 || n == 2 {
|
|
return n
|
|
}
|
|
var a = 1
|
|
var b = 2
|
|
for _ in 3 ... n {
|
|
(a, b) = (b, a + b)
|
|
}
|
|
return b
|
|
}
|
|
|
|
@main
|
|
enum ClimbingStairsDP {
|
|
/* Driver Code */
|
|
static func main() {
|
|
let n = 9
|
|
|
|
var res = climbingStairsDP(n: n)
|
|
print("Climbing \(n) stairs, there are \(res) different solutions")
|
|
|
|
res = climbingStairsDPComp(n: n)
|
|
print("Climbing \(n) stairs, there are \(res) different solutions")
|
|
}
|
|
}
|