遞迴與組合

福利彩票和體育彩票近兩年比較火暴，相應在vb論壇上大家討論也較多。其實選擇彩票與集合選擇子集相同道理。下面給出一種vb的遞迴演算法（雖然明知存入陣列會加快運算速度，但最終也沒能滿意地實現，請大家多多指教。另外，效率確實不高）

option explicit

private sub command1_click()

dim temp, i as long, starttime as long, endtime as long

starttime = timer

temp = cmn(22, 6)

endtime = timer

open "d:\mofn.txt" for binary as #1 '寫入檔案

put #1, , temp

close #1

msgbox ubound(split(temp, vbcrlf)) + 1 & " 種組合", 64, "共用時 " & endtime - starttime & " 秒" '計算組合可能情況和耗時

end sub

function cmn(byval m as integer, byval n as integer) as string ' select n number from 1～m

dim a() as string, temp as string, i as long

redim a(1 to m) '定義陣列

for i = 1 to m

a(i) = i

if m = 3 then

if n = 1 then cmn = 1 & vbcrlf & 2 & vbcrlf & 3

if n = 2 then cmn = "1,2" & vbcrlf & "1,3" & vbcrlf & "2,3"

if n = 3 then cmn = "1,2,3"

elseif m > 3 then

if n = 1 then cmn = join(a, vbcrlf)

if n = m then cmn = join(a, ",")

if n > 1 and n < m then

temp = cmn(m - 1, n - 1)

'debug.print m - 1 & "," & n - 1 & vbcrlf & "----------------" & vbcrlf & temp & vbcrlf & "---------------------------" & vbcrlf '可以在立即視窗檢視演算法過程

temp = replace(temp, vbcrlf, "," & m & vbcrlf) & "," & m

cmn = cmn(m - 1, n) & vbcrlf & temp

end if

end function

下面給出利用集合實現不重複隨機選取某幾個號碼，這個函式也可用來實現陣列全部元素的隨機排列。

function getone(byval m as integer, byval n as integer) as string ' one random option to select n number from 1～m without repeat number

dim a() as string, temp as new collection, i as long, tempi as long

redim a(1 to n) '定義陣列

for i = 1 to m

temp.add i '可以根據需要更改

randomize

for i = 1 to n

tempi = int(rnd * temp.count) + 1

a(i) = temp(tempi)

temp.remove tempi

getone = join(a, ",")

set temp = nothing

erase a

end function

private sub command2_click()'演示用法

msgbox getone(30, 8), 64, "30選8 的一種選法"

msgbox getone(100, 100), 64, "1 到100 的一種不重複全排列"

end sub

遞迴與組合

遞迴列印組合

組合與全排列非遞迴演算法

排列與組合的Java遞迴實現

遞迴與組合

遞迴列印組合

組合與全排列非遞迴演算法

排列與組合的Java遞迴實現

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