#include <stdio.h>void main() { int i,a,b,c; int count=0; int x; scanf("%d",&x); for(i=0;i<1000;i++) { a=i/100; b=i%100/10; c=i%10; if (a+b+c==x) count++; } printf("count=%d",count); }
Function getnum(ByVal x As Integer) As Integer Dim i As Integer For i = 0 To 999 If i Mod 10 + (i \ 10) Mod 10 + i \ 100 = x Then getnum = getnum + 1 Next End Function
有没有效率更高的算法?Function getnum(ByVal x As Integer) As Integer getnum = Array(1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 63, 69, 73, 75, 75, 73, 69, 63, 55, 45, 36, 28, 21, 15, 10, 6, 3, 1)(x) End Function
to northwolves(狼行天下) vb不太熟,不过感觉Array的初始化和对index检索似乎都有改进的余地 :) 试了一下: Public Function getnum(ByVal x As Integer) As Integer Dim a() As Integer = {1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 63, 69, 73, 75, 75, 73, 69, 63, 55, 45, 36, 28, 21, 15, 10, 6, 3, 1} Return a(x) End Function Public Function getnum2(ByVal x As Integer) As Integer 'Dim a() As Integer = {1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 63, 69, 73, 75, 75, 73, 69, 63, 55, 45, 36, 28, 21, 15, 10, 6, 3, 1} If x < 10 Then Return (x + 1) * (x + 2) / 2 If x > 17 Then Return (28 - x) * (29 - x) / 2 If x = 13 Or x = 14 Then Return 75 If x = 12 Or x = 15 Then Return 73 If x = 11 Or x = 16 Then Return 69 If x = 10 Or x = 17 Then Return 63 End Function For j = 0 To 100000000 'getnum(27) 24秒 'getnum(17) 24秒 'getnum2(27) 20秒 'getnum2(17) 4秒 Next有没有效率更高的算法? :)
我来解释一下 , 可能是那两个算式把人搞糊涂了。实际上由于那个数列有较特殊的关系,对于x<10时,f(x)=f(x-1)+x ,故写成了那个形式。 之所以比较27和17,因为那是该算法中可能的,最慢的值。其实在这个case中,象 If x = 13 Or x = 14 那样直接的一个个写出来,效果应该更好另外,象northwolves(狼行天下) 那样用Array,但将他声明为静态的,只初始化一次,可能就是最快的,Vb这个我不太会写,有兴趣的可以试试,别忘了告诉一下结果 :)
{
int i,a,b,c;
int count=0;
int x;
scanf("%d",&x);
for(i=0;i<1000;i++)
{
a=i/100;
b=i%100/10;
c=i%10;
if (a+b+c==x)
count++;
}
printf("count=%d",count);
}
Dim i As Integer
For i = 0 To 999
If i Mod 10 + (i \ 10) Mod 10 + i \ 100 = x Then getnum = getnum + 1
Next
End Function
getnum = Array(1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 63, 69, 73, 75, 75, 73, 69, 63, 55, 45, 36, 28, 21, 15, 10, 6, 3, 1)(x)
End Function
vb不太熟,不过感觉Array的初始化和对index检索似乎都有改进的余地 :)
试了一下:
Public Function getnum(ByVal x As Integer) As Integer
Dim a() As Integer = {1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 63, 69, 73, 75, 75, 73, 69, 63, 55, 45, 36, 28, 21, 15, 10, 6, 3, 1}
Return a(x)
End Function
Public Function getnum2(ByVal x As Integer) As Integer
'Dim a() As Integer = {1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 63, 69, 73, 75, 75, 73, 69, 63, 55, 45, 36, 28, 21, 15, 10, 6, 3, 1}
If x < 10 Then Return (x + 1) * (x + 2) / 2
If x > 17 Then Return (28 - x) * (29 - x) / 2
If x = 13 Or x = 14 Then Return 75
If x = 12 Or x = 15 Then Return 73
If x = 11 Or x = 16 Then Return 69
If x = 10 Or x = 17 Then Return 63
End Function
For j = 0 To 100000000
'getnum(27) 24秒
'getnum(17) 24秒
'getnum2(27) 20秒
'getnum2(17) 4秒
Next有没有效率更高的算法? :)
可能是那两个算式把人搞糊涂了。实际上由于那个数列有较特殊的关系,对于x<10时,f(x)=f(x-1)+x ,故写成了那个形式。
之所以比较27和17,因为那是该算法中可能的,最慢的值。其实在这个case中,象 If x = 13 Or x = 14 那样直接的一个个写出来,效果应该更好另外,象northwolves(狼行天下) 那样用Array,但将他声明为静态的,只初始化一次,可能就是最快的,Vb这个我不太会写,有兴趣的可以试试,别忘了告诉一下结果 :)