BigNumber_1

A - BigNumber_1

Time Limit:1000MS     Memory Limit:32768KB     64bit IO Format:%I64d & %I64u

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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.
        
        
        
        
        
        

 

PS：大数相加+斐波那契数列

代码：

#include<iostream>
#include<string>
using namespace std;

int ns[2100] = { 0 };

string add(string sa, string sb)
{
	string sa1, sb1;
	sa1 = sa;
	sb1 = sb;
	int la = sa.length();
	int lb = sb.length();
	if (la < lb)
	{
		string tmps = sa;
		sa = sb;
		sb = tmps;
		int tmpi;
		tmpi = la;
		la = lb;
		lb = tmpi;
	}
	string st = "";
	for (int j = lb; j < la; ++j)
	{
		st += '0';
	}
	st += sb;
	sb = st;
	int num = 0, k = 0;
	for (int m = la - 1; m >= 0; --m)
	{
		int sum = (sa[m] - '0') + (sb[m] - '0') + num;
		ns[k++] = sum % 10;
		num = sum / 10;
	}
	if (num > 0)
	{
		ns[k++] = num;
	}
	string str = "";
	for (int j = k - 1; j >= 0; --j)
	{
		str += (ns[j] + '0');
	}
	return str;
}

int main()
{
	string f[7101];
	f[1] = f[2] = f[3] = f[4] = "1";
	for (int i = 5; i < 7101; ++i)
	{
		f[i] = add(add(f[i - 1], f[i - 2]), add(f[i - 3], f[i - 4]));
	}
	int num;
	while (cin >> num)
	{
		cout << f[num] << endl;
		//cout << f[num].length() << endl;
	}

	return 0;
}