求得到一个字符串@“absdfasdfsdfdsafsd....”所有的排列

 //得到一个字符串@“absdfasdfsdfdsafsd....”所有的排列   length！/(（相同项）！*（相同项）！)

-(int )numberOfstring:(NSString*)str
   // NSString *str [email protected]"adfsadfasdfasdfsadfsdaxfgghfgjtyy";
    int sumlength = str.length;//所有字符的个数
    NSString *mystr = @"abcdefghijklmnopqrstuvwxyz";
    NSMutableArray *sameCharNumberArr = [NSMutableArray array];
    for (int i=0; i<mystr.length; i++) {
        NSString *charstr = [mystr substringFromIndex:i];
        int number = [[str componentsSeparatedByString:charstr]count]-1;
        if (number>1) {
            [sameCharNumberArr addObject:[NSNumber numberWithInt:number]];
        }
    }
    int textsum=1;
    for (NSNumber *nub in sameCharNumberArr) {
        textsum *= fac([nub intValue]);
    }

    int numberOfstr =  fac(sumlength)/textsum;
    NSLog(@"所有排列的个数为 %d",numberOfstr);
  return numberOfstr;
}

int fac(int n)
{
    int rs=1;
    while(n>1)
        rs*=n--;
    return rs;
}