本文格式為Word版，下載可任意編輯——java算法實現排列組合的方法介紹java算法實現排列組合的方法介紹

一.利用二進制狀態法求排列組合，此種方法對比輕易懂，但是運行效率不高，小數據排列組合可以使用代碼如下:

importjava.util.Arrays;

//利用二進制算法舉行全排列

//count1:170187

//count2:291656

publicclasstest

publicstaticvoidmainString[]args

longstart=System.currentTimeMillis;

count2;

longend=System.currentTimeMillis;

System.out.printlnend-start;

privatestaticvoidcount2

int[]num=newint[]1,2,3,4,5,6,7,8,9;

forinti=1;iMath.pow9,9;i++

Stringstr=Integer.toStringi,9;

intsz=str.length;

forintj=0;j9-sz;j++

str=0+str;

char[]temp=str.toCharArray;

Arrays.sorttemp;

Stringgl=newStringtemp;

if!gl.equals012345678

continue;

Stringresult=;

forintm=0;mstr.length;m++

result+=num[Integer.parseIntstr.charAtm+];

System.out.printlnresult;

publicstaticvoidcount1

int[]num=newint[]1,2,3,4,5,6,7,8,9;

int[]ss=newint[]0,1,2,3,4,5,6,7,8;

int[]temp=newint[9];

whiletemp[0]9

temp[temp.length-1]++;

forinti=temp.length-1;i0;i--

iftemp[i]==9

temp[i]=0;

temp[i-1]++;

int[]tt=temp.clone;

Arrays.sorttt;

if!Arrays.equalstt,ss

continue;

Stringresult=;

forinti=0;inum.length;i++

result+=num[temp[i]];

System.out.printlnresult;

二.用遞歸的思想來求排列跟組合，代碼量對比大代碼如下:

packagepractice;

importjava.util.ArrayList;

importjava.util.List;

publicclassTest1

/**

*@paramargs

*/

publicstaticvoidmainString[]args

//TODOAuto-generatedmethodstub

Object[]tmp=1,2,3,4,5,6;

//ArrayList

rs=RandomCtmp;

ArrayList

rs=cmntmp,3;

forinti=0;irs.size;i++

//System.out.printi+=;

forintj=0;jrs.geti.length;j++

System.out.printrs.geti[j]+,;

System.out.println;

//求一個數組的任意組合

staticArrayList

RandomCObject[]source

ArrayList

result=newArrayList

;

ifsource.length==1

result.addsource;

else

Object[]psource=newObject[source.length-1];

forinti=0;ipsource.length;i++

psource[i]=source[i];

result=RandomCpsource;

intlen=result.size;//fn組合的長度

result.addnewObject[]source[source.length-1];

forinti=0;ilen;i++

Object[]tmp=newObject[result.geti.length+1];

forintj=0;jtmp.length-1;j++

tmp[j]=result.geti[j];

tmp[tmp.length-1]=source[source.length-1];

result.addtmp;

returnresult;

staticArrayList

cmnObject[]source,intn

ArrayList

result=newArrayList

;

ifn==1

forinti=0;isource.length;i++

result.addnewObject[]source[i];

elseifsource.length==n

result.addsource;

else

Object[]psource=newObject[source.length-1];

forinti=0;ipsource.length;i++

psource[i]=source[i];

result=cmnpsource,n;

ArrayList

tmp=cmnpsource,n-1;

forinti=0;itmp.size;i++

Object[]rs=newObject[n];

forintj=0;jn-1;j++

rs[j]=tmp.geti[j];

rs[n-1]=source[source.length-1];

result.addrs;

returnresult;

三.利用動態規劃的思想求排列和組合代碼如下:

packageAcm;

//強大的求組合數

publicclassMainApp

publicstaticvoidmainString[]args

int[]num=newint[]1,2,3,4,5;

Stringstr=;

//求3個數的組合個數

//count0,str,num,3;

//求1-n個數的組合個數

count10,str,num;

privatestaticvoidcount1inti,Stringstr,int[]num

ifi==num.length

System.out.printlnstr;

return;

count1i+1,str,num;

count1i+1,str+num[i]+,,num;

privatestaticvoidcountinti,Stringstr,int[]num,intn

ifn==0

System.out.printlnstr;

return;

ifi==num.length

return;

counti+1,str+num[i]+,,num,n-1;

counti+1,str,num,n;

下面是求排列代碼如下:

packageAcm;

//求排列，求各種排列或組合后排列

importjava.util.Arrays;

importjava.util.Scanner;

publicclassDemo19

privatestaticbooleanf[];

publicstaticvoidmainString[]args

Scannersc=newScannerSystem.in;

intsz=sc.nextInt;

forinti=0;isz;i++

intsum=sc.nextInt;

f=newboolean[sum];

Arrays.fillf,true;

int[]num=newint[sum];

forintj=0;jsum;j++

num[j]=j+1;

intnn=sc.nextInt;

Stringstr=;

countnum,str,nn;

/**

*

*@paramnum表示要排列的'數組

*@paramstr以排列好的字符串

*@paramnn剩下需要排列的個數，假設需要全排列，那么nn為數組長度

*/

pr