iTheresaApocalypse @ 2023-02-14 10:52:36

#include<bits/stdc++.h>
using namespace std;
#define maxn 2000
int n;
struct Bigint{

    int len,a[maxn];

    Bigint(int x=0)
    {
        memset(a,0,sizeof(a));
        for(len=1;x;len++)
        {
            a[len]=x%10;
            x/=10;
        }
        len--; 
    }

    int &operator[](int i)
    {
        return a[i];
    }

    void flatten(int l)
    {
        len = l;
        for(int i=1;i<=len;i++)
            a[i+1]+=a[i]/10,a[i]%=10;
        for(;!a[len];)
            len--;
    } 

    void print()
    {
        for(int i=max(len,1);i>=1;i--)
            printf("%d",a[i]);
    }
};

Bigint operator+(Bigint a,Bigint b)
{
    Bigint c;
    int len=max(a.len,b.len);
    for(int i=1;i<=len;i++)
        c[i]+=a[i]+b[i];
    c.flatten(len+1);
    return c;

}
int main()
{

    cin>>n;
    Bigint f[5050];
    f[1] = Bigint(1);
    f[2] = Bigint(2);

    for(int i=3;i<=n;i++)
    {
        f[i]=f[i-1]+f[i-2];
    }

    f[n].print();
    return 0;
} 

by ud2_ @ 2023-02-14 11:03:48

STATUS_ACCESS_VIOLATION.

在这里是因为栈空间不够；Windows 下默认分配的 2 MB 栈放不下 40 MB 的数组 f。

by iTheresaApocalypse @ 2023-02-14 14:12:11

@ud2_ 感谢！

by Roger_Spencer @ 2023-03-20 09:25:30

高精度+滚动数组+dP

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源码

#include <bits/stdc++.h>

using namespace std;

#define LL long long

#define endl "\n"

const int N = 1e5 + 10;

const int M = 5510;

int dp[N];

vector<int> add(vector<int> &A, vector<int> &B)
{
    if (A.size() < B.size()) return add(B, A);

    vector<int> C;
    int t = 0;
    for (int i = 0; i < A.size(); i ++ )
    {
        t += A[i];
        if (i < B.size()) t += B[i];
        C.push_back(t % 10);
        t /= 10;
    }

    if (t) C.push_back(t);
    return C;
}

void solve()
{
    int n;
    cin >> n;

    if ( n == 1) 
    {
        cout << 1 << endl;
        return;
    }

    vector<int> A, B, C, D;

    A.push_back(1);
    B.push_back(1);
    for (int i = 2; i <= n; i ++ )
    {
        C = add(A, B);
        A = B;
        B = C;
    }

    for (int i = C.size() - 1; i >= 0; i -- ) cout << C[i];

    cout << endl;

}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);

    solve();

    return 0;
}