objective c - Consecutive Primes Challenge -

i working on consecutive primes challenge @ codeeval.com , can't pass automatic grader. think getting correct results possibly missing edge cases. tried recursion couldn't work , slow. figured out solution creating 2 arrays , odd numbers. please let me know if viable solution , if can see mistake.

here challenge description:

alice has number of n beads, , each bead has number 1 n painted on it. make necklace out of beads, special requirement: 2 beads next each other on necklace must sum prime number. alice needs calculate how many ways possible so.

for example:

n = 4

there 2 possible ways build necklace. note last bead connects first bead.

1 2 3 4 1 4 3 2 

note: necklace should unique. example: 1 2 3 4 same 2 3 4 1 , 3 4 1 2 , 4 1 2 3.

the code has c , obj-c because of limitation in codeeval.com auto grader. here code:

    bool isprime(int number){         for(int = 2;i<(int)(number/2)+1;i++){             if (number%i == 0) {                 return false;             }         }         return true;     }      bool iseven(int number)     {         if(number%2==0){             return true;         }         return false;     }       nsmutablearray *createevennumbersarray(int num)     {         nsmutablearray *evennumarray = [[nsmutablearray alloc]initwithcapacity:num];         (int i=2; i<=num; i+=2) {             [evennumarray addobject:[nsnumber numberwithint:i]];         }         return evennumarray;     }      nsmutablearray *createoddnumbersarray(int num)     {         nsmutablearray *oddnumarray = [[nsmutablearray alloc]initwithcapacity:num];         (int i=3; i<=num; i+=2) {             [oddnumarray addobject:[nsnumber numberwithint:i]];         }         return oddnumarray;     }        int calculateconsecutive(int input)     {         int count = 0;         bool evenfound = no;         bool oddfound = no;         nsmutablearray *oddnumarray = createoddnumbersarray(input); //creates odd number array possiblities         nsmutablearray *evennumarray = createevennumbersarray(input); // create number array possibilities         nsmutablearray *necklace = [[nsmutablearray alloc]init];         [necklace addobject:[nsnumber numberwithint:1]]; // start necklace 1 rid of duplicate necklaces         (int = 2; i<=input; i+=2) { // goes through possibilities second bit create necklase             nsmutablearray *tempoddnumarray = [oddnumarray mutablecopy]; // populate odd number array             nsmutablearray *tempevennumarray = [evennumarray mutablecopy]; // puplate number array             if(isprime([[necklace lastobject] intvalue] + i)){                 [tempevennumarray removeobject:[nsnumber numberwithint:i]]; //remove number added necklase                 [necklace addobject:[nsnumber numberwithint:i]];                 while ([necklace count]<=input) { // start creating necklace after 2 numbers added                     oddfound = no;                     evenfound = no;                     for(nsnumber *oddnumber in tempoddnumarray){ // find odd number possibility numbers left in array                         if(isprime([[necklace lastobject] intvalue] + oddnumber.intvalue)){                             [necklace addobject:oddnumber];                             oddfound = yes;                             break;                         }                     }                     if (!oddfound) {                         break;                     }else{                         [tempoddnumarray removeobject:[necklace lastobject]];                     }                     for(nsnumber *evennumber in tempevennumarray){ // find odd number possibility numbers left in array                         if(isprime([[necklace lastobject] intvalue] + evennumber.intvalue)){                             [necklace addobject:evennumber];                             evenfound = yes;                             break;                         }                     }                     if (!evenfound) {                         break;                     }else{                         [tempevennumarray removeobject:[necklace lastobject]];                     }                     if (([tempoddnumarray count] == 0) || ([tempevennumarray count] == 0) ){                         break;                     }                  }             }             if (([necklace count] == input) && (isprime([[necklace lastobject] intvalue]+[[necklace firstobject] intvalue]))) {                 // check make sure necklace full , if sum of last number , first number prime                 count= count + 1;             }             nslog(@"%@",necklace);              [necklace removeallobjects];             [necklace addobject:[nsnumber numberwithint:1]];         }         return count;     }      -(void)primesmain     {         int necklacecount = 0;         int input = 18;         if (iseven(input)) {             necklacecount = calculateconsecutive(input);         }         nslog(@"%d",necklacecount);     }  -(void)viewdidload {      [self primesmain]; } 

i apologize regarding crossposting code review site. wanted suggestions on code , find error. let me know , delete post on 1 of forums.

thank you!

=============== update

i found error in previous code. didn't iterate through possibilities. rewrote code using recursion. getting different answers still not correct. codeeval using 8 test value , 0 result. wonder if not correct. here updated code

nsuinteger count=0; // using global variable don't have deal counting in recursion anyway  bool isprime(int number){     for(int = 2;i<(int)(number/2)+1;i++){         if (number%i == 0) {             return false;         }     }     return true; }  bool iseven(int number) {     if(number%2==0){         return true;     }     return false; }  void calculatenumnecklaces(int numofbeads, nsmutablearray *beadsarray, nsmutablearray *necklace) {      if ([beadsarray count] == 1) {         nslog(@"%@",necklace);          if((isprime([[necklace lastobject] intvalue] + [[beadsarray lastobject] intvalue]) && (isprime([[necklace objectatindex:0] intvalue] + [[beadsarray lastobject] intvalue])))){             count +=1;         }         //return 1;     }else{         int previousnumber = [[necklace lastobject] intvalue];         int startpos = 0;         if (iseven(previousnumber)){             if (iseven([[beadsarray objectatindex:0] intvalue])) {                 startpos = 1; //it itterate through odd numbers in bead array starting position odd number             }         }else {             if (!iseven([[beadsarray objectatindex:0] intvalue])) {                 startpos = 1; //it itterate through numbers in bead array starting position odd number             }         }         (int pos = startpos; pos < [beadsarray count]; pos+=2) {             if (isprime(previousnumber  + [[beadsarray objectatindex:pos] intvalue])) {                 nsmutablearray *tempnecklace = [necklace mutablecopy];                 [tempnecklace addobject:[beadsarray objectatindex:pos]];                 nsmutablearray *temparray = [beadsarray mutablecopy];                 [temparray removeobjectatindex:pos];                 //nslog(@"%@",necklace);                 calculatenumnecklaces(numofbeads, temparray, tempnecklace);             }         }      }       //return 0; }    -(void)primesmain {     int input = 6;     if (iseven(input)) {         nsmutablearray *beadsarray =[[nsmutablearray alloc] init];         (int = 2; i<=input; i++) {             [beadsarray addobject:[nsnumber numberwithint:i]];         }         nsmutablearray *necklace = [[nsmutablearray alloc]init];         [necklace addobject:[nsnumber numberwithint:1]];         calculatenumnecklaces(input, beadsarray, necklace);     }     nslog(@"%d",count); } 

this program finding how many possibilities of consecutive numbers(rummy in cards) in array....

program:

#include<iostream.h> #include<conio.h> void main()    {       int a[10],j,i,n,c,d;       cin>>n;        for(i=1;i<=n;i++)          {            cin>>a[i];          }  for(i=1;i<=n;i++)   {     for(j=1;j<=n-i;j++)       {          if(a[j]>a[j+1])           {             int temp;             temp=a[j];             a[j]=a[j+1];              a[j+1]=temp;            }        }        }    for(j=1;j<=n;j++)     {       c=a[j]-a[j+1];       d=a[j]-a[j+2];           if(c==-1 && d==-2)             {                  cout<<a[j]<<a[j+1]<<a[j+2];                }           cout<<"\n";       }     getch();    }        output:          input:              a[i]={4,3,6,7,8,5}          output:                   345                   456                   567                   678