hello-algo/codes/swift/chapter_computational_complexity/recursion.swift

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/**
* File: recursion.swift
* Created Time: 2023-09-02
* Author: nuomi1 (nuomi1@qq.com)
*/
/* */
func recur(n: Int) -> Int {
//
if n == 1 {
return 1
}
//
let res = recur(n: n - 1)
//
return n + res
}
/* */
func tailRecur(n: Int, res: Int) -> Int {
//
if n == 0 {
return res
}
//
return tailRecur(n: n - 1, res: res + n)
}
/* */
func fib(n: Int) -> Int {
// f(1) = 0, f(2) = 1
if n == 1 || n == 2 {
return n - 1
}
// f(n) = f(n-1) + f(n-2)
let res = fib(n: n - 1) + fib(n: n - 2)
// f(n)
return res
}
@main
enum Recursion {
/* Driver Code */
static func main() {
let n = 5
var res = 0
res = recursion.recur(n: n)
print("\n递归函数的求和结果 res = \(res)")
res = recursion.tailRecur(n: n, res: 0)
print("\n尾递归函数的求和结果 res = \(res)")
res = recursion.fib(n: n)
print("\n斐波那契数列的第 \(n) 项为 \(res)")
}
}