10229 - Modular Fibonacci

[akdwivedi]

Hi !! here is my code , I am getting wrong answer ..can anybody help me.......

what is wrong ??


#include<iostream>
#include<cstdio>
#include<math.h>
using namespace std;
long long int Fib(long long int n)
{
long long int i=1,h=1;
long long int j =0,k=0,t;
while (n > 0) {
if (n%2 == 1) {
t = j*h;
j = i*h + j*k + t;
i = i*k + t;
}
t = h*h;
h = 2*k*h + t;
k = k*k + t;
n=(int)floor(n/2.0);
}
return j;
}
int main()
{
long long int n,m;
while(scanf("%lld%lld",&n,&m)!=EOF)
{
printf("%lld\n",Fib(n)%((int)pow(2,m)));
}
return 0;
}


even this algo is work on O(lon(n));;;;.....reaply.. soon

thanks..

[898989]

Salamo Aleko
You can visit steven halim site for uva problem solving
And find the implemenation in his explantation
I used it and get ac in 10 minutes.
Sorry i do not know a reference. If you got a link..give it to us.

[joy]

I got WA.....
plz give me some input/ output.....
here is my code:

Code: Select all

remove after ACC

plz help..........

[Jan]

Check the samples...

Input:

Code: Select all

288 6
15006 1
22929 1
4596 1

Output:

Code: Select all

0
0
0
0

Hope these help.

[joy]

thanks Jane ...

I got ACC now

[jojo]

Hi
Could anyone tell me how to solve tihs problem ?
I've got our Fn by using O(lg) algorithm and I know that
(a*b*c)%n==((a%n)*(b%n)*(c%n))%n
but I don't know how to use it?
Should I find prime factors of this number and use them to calculate Fn%m - I think that 2147483647th fibbonacii is too big for doing this .
I'm confused.
plx help me
jojo

[joy]

Hi
Could anyone tell me how to solve tihs problem ?
I've got our Fn by using O(lg) algorithm and I know that
(a*b*c)%n==((a%n)*(b%n)*(c%n))%n
but I don't know how to use it?
Should I find prime factors of this number and use them to calculate Fn%m - I think that 2147483647th fibbonacii is too big for doing this .
I'm confused.
plx help me
jojo

hi,

Code: Select all

Sequence of Fibonacci numbers:
Fibo(i)   : 1 1 2 3 5 8 13 21 34 55 89 144 233...
Sequence of Fibonacci numbers mod 2:
Fibo(i)%2 : 1 1 0 1 1 0 1 1 0...
Sequence of Fibonacci numbers mod 3:
Fibo(i)%3 : 1 1 2 0 2 2 1 0 1 1 2 0...

You dont need to use n time loop to solve this problem

Hope it helps..

[code_man]

I have runtime error, but I don't know why? Somebody can tell me what's wrong with this code? :

Code: Select all

#include<iostream>
using namespace std;

int fibon(int a);
int potega(int b);

int main()
{
  int n, m;
  while(cin>>n>>m)
   { cout<<fibon(n)%potega(m)<<"\n"; }
}
/*****************************************************/
int fibon(int a)
{
 if(a==0) return 0;
 if(a<1)  return 1;
 else
 return (fibon(a-1)+ fibon(a-2));     
}

int potega(int b)
{
  int pomoc=1;
  for(int i=0; i<b; i++)
   { pomoc*=2; }
    
 return pomoc;     
}

[newton]

i cant find the point like jojo.
may you help explaining it elaborately....



thanx

[mf]

Read previous posts in this thread.

[ifox]

yes, long long will get ac

at a rough scan on your code, what i think is, there seems not a need to use long double, you can make it to int, or long long. then, your program may be better, at least need not worry about floating point error. though i cannot tell you whether it will get AC

[fR0D]

can somebody please point out why am i getting WA?

Code: Select all

#include<iostream>
using namespace std;

long long p;

long long pow(int i,int j)
{
    long long val=1;
    int k;
    for (k=1;k<=j;k++)
        val=val*i;
    return val;
}

long long conquer_fibonacci(long long n)
{
     long long i,h,j,k,t;
     i=h=1;
     j=k=0;
     while(n>0)
     {
      if(n%2==1)
      {
       t=j*h;
       j=((i*h)%p + (j*k)%p +t%p)%p;
       i=i*k + t;
      }
      t=h*h;
      h=2*k*h + t;
      k=k*k + t;
      n=(long long) n/2;
     }
     return j;
}

int main()
{
    long long n,res,m;
    while(scanf("%lld%lld",&n,&m)!=EOF)
    {
     p=pow(2,m);
     res=conquer_fibonacci(n);
     printf("%lld\n",res%pow(2,m));
    }
     return 0;
}

[helloneo]

can somebody please point out why am i getting WA?

Sometimes k and t can be very big.. so it may cause overflow error..

[fR0D]

so how can i avoid that???

[carliros]

Input
11 7
11 6
2147483647 2
0 0
2147483647 0
2147483647 19

output
89
25
1
0
0
325917