Go 语言解面试题1

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/* 比较一下

:http://blog.csdn.net/iilovetopview/article/details/43745059

go的运算效率逊于D(LDC 编译器0.15.1(LLVM3.6 ,MSVC64))。

用“数学公式”法解下题：

有一个整数n,写一个函数f(n),返回0到n之间出现的"1"的个数。
比如f(13)=6,现在f(1)=1,问下一个最大的f(n)=n的n是什么？

package mainimport ("fmt""time""math") var aa map[int]intvar Ac []intfunc main() {fmt.Println("(go Language)  Please wait for some minutes,will found Next Fn(n) = n ,the n is:")n := 1count :=0pos := 0t :=time.Now()for n =1;n<200000;n++ {aa = make(map[int]int)    Ac = make([]int,10)pos = Fn(n) if n == pos {count++fmt.Println("n is :",n," Fn(n) is :",pos)if(count >1) {break}}}fmt.Println("time is :",time.Now().Sub(t).String())fmt.Println(n," stop")fmt.Println("test 199981 is :",Fn_test(199981))} func Fn(n int) int {i:=0y:=0for x :=n;x>=1;x/=10 {y=x%10aa[i] =yAc[i] =yi++}Ac = Ac[0:i]  //关键m := len(Ac)-1h :=aa[m]if( n%gPow(m) == 0) {return fnA(h,m)}else{ return  fnA(h,m)+fnB(m-1)}}func fnA(h int,m int) int {if(h == 0){return 0}else if h==1 {if(m == 0) {return 1} else{ return  m*gPow(m-1)+1}}else {if(m == 0) {return 1} else{ return  gPow(m)+h*m*gPow(m-1)}}} func fnB(m int) int {   ..... //代码略return  sum + fnB(m-1)}func gPow(m int) int {return int(math.Pow10(m)) }/*－－－－－－－－－－－－测试－－－－－－－－－－－－－*/func Fn_test(n int) int { total:= 0for i:=0;i<=n;i++ {total += Count(i)}return total}func Count(n int) int {num:=0for t:= n;t >=1;t=t/10 {if(t%10 == 1) {num++}}return num}

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