Scala语言学习-05-递归和尾递归效率对比

一、测试环境

名称	版本
操作系统	win10
CPU	12th Gen Intel Core i7-12700H
内存	16G
JDK	1.8.0_171
Scala	3.1.2

二、代码

import java.util.Date

object TestRecursion {
    
    def main(args: Array[String]): Unit = {
    
        val TempNum: Long = 12L
        ComputeProcedureTime(Factorial, TempNum,"递归：")
        ComputeProcedureTime(TailFactorial, TempNum,"尾递归：")
    }
    
    def ComputeProcedureTime(Func :Long => Long, Param: Long, Info: String): Unit = {
    
        println("++++++++++++++++++++++++++++")
        println(Info)
        var start_time =new Date().getTime
        println(Func(Param))
        var end_time =new Date().getTime
        println(s"Elapsed Time : ${
      end_time-start_time} ms")
    }
    
    def Factorial(Num: Long): Long = {
    
        if (Num == 1){
    
            Num
        }
        else {
    
            Num * Factorial(Num - 1)
        }
    }
    
    def TailFactorial(Num: Long): Long = {
    
        def Loop(Num: Long,Res: Long): Long = {
    
            if(Num == 1){
    
                Res
            }
            else{
    
                Loop(Num - 1, Res * Num)
            }
        }
        Loop(Num, 1)
    }
}

三、运行结果

++++++++++++++++++++++++++++
递归：
479001600
Elapsed Time : 1 ms
++++++++++++++++++++++++++++
尾递归：
479001600
Elapsed Time : 0 ms

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