zoj 1828 Fibonacci Numbers

ZOJ Problem Set - 1828

Fibonacci Numbers

---

Time Limit: 2 Seconds      Memory Limit: 65536 KB

---

A Fibonacci sequence is calculated by adding the previous two members of the sequence, with the first two members being both 1.

f(1) = 1, f(2) = 1, f(n > 2) = f(n - 1) + f(n - 2)

Your task is to take a number as input, and print that Fibonacci number.

Sample Input

100

Sample Output

354224848179261915075

Note:

No generated Fibonacci number in excess of 1000 digits will be in the test data, i.e. f(20) = 6765 has 4 digits.

#include<iostream>
using namespace std;
int a[6001][1001];
int getmaxlen(int fir,int sec)
{
    int i,j;
    for(i=1000;a[fir][i]==0;i--);
    for(j=1000;a[sec][j]==0;j--);
    if(i>=j)
        return i;
    else
        return j;
}
void fibonacci(int n)
{
    int i,j,len;
    int c=0;
    for(j=2;j<n;j++)
    {
        len=getmaxlen(j-1,j-2);
        for(i=0;i<=len+1;i++)
        {
            a[j][i]=(a[j-1][i]+a[j-2][i]+c)%10;
            c=(a[j-1][i]+a[j-2][i]+c)/10;
        }
    }
}
int main()
{
    int n,i,j;
    memset(a,0,sizeof(a));
    a[0][0]=1;
    a[1][0]=1;
    while(cin>>n)
    {    
        for(i=1000;a[n-1][i]==0;i--);
        if(i<0)
        {    fibonacci(n);
            for(i=1000;a[n-1][i]==0;i--);
        }
        for(j=i;j>=0;j--)
            cout<<a[n-1][j];
        cout<<endl;
    }
    return 0;
}

  注：不能直接用公式，因为当数较大时用int型无法表示，这里一位一位计算，然后存储到数组中，最后输出。