HDU1250--Hat's Fibonacci

Hat's Fibonacci
Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 5270 Accepted Submission(s): 1764


Problem Description
A Fibonacci sequence is calculated by adding the previous two members the sequence, with the first two members being both 1.
F(1) = 1, F(2) = 1, F(3) = 1,F(4) = 1, F(n>4) = F(n - 1) + F(n-2) + F(n-3) + F(n-4)
Your task is to take a number as input, and print that Fibonacci number.


Input
Each line will contain an integers. Process to end of file.


Output
For each case, output the result in a line.


Sample Input
100


Sample Output
4203968145672990846840663646


Note:
No generated Fibonacci number in excess of 2005 digits will be in the test data, ie. F(20) = 66526 has 5 digits.


Author
戴帽子的


Recommend
Ignatius.L

#include<cstdio>
#include<cmath>
#include<string>
#include<iostream>
using namespace std;
 
string sum(string s1,string s2)   
{   
     if(s1.length()<s2.length())   
     {   
          string temp=s1;   
          s1=s2;   
          s2=temp;   
     }   
     for(int i=s1.length()-1,j=s2.length ()-1;i>=0;i--,j--)   
     {   
          s1[i]=char(s1[i]+(j>=0?s2[j]-'0':0));   
          if(s1[i]-'0'>=10)   
          {   
              s1[i]=char((s1[i]-'0')%10+'0');   
              if(i)   
                   s1[i-1]++;   
              else  
                   s1='1'+s1;   
          }   
     }   
     return s1;   
}   
 
int main()
{
    string str[10000];
    str[1]="1";
    str[2]="1";
    str[3]="1";
    str[4]="1";
    int n;
    for(n=5;n<7039;n++)
    {
        str[n]=sum(sum(str[n-1],str[n-2]),sum(str[n-3],str[n-4]));
    }
    int x;
    while(scanf("%d",&x)!=EOF)
    {
        cout<<str[x]<<endl;
    }
    return 0;
}