```cpp
#include<bits/stdc++.h>
using namespace std;
int len=1,f[5005][5005];
void add(int k){
for(int i=1;i<=len;i++)
f[k][i]=f[k-1][i]+f[k-2][i];
for(int i=1;i<=len;i++)
if(f[k][i]>=10){
f[k][i+1]+=f[k][i]/10;
f[k][i]=f[k][i]%10;
if(f[k][len+1])len++;
}
}
int main(){
int n;
cin>>n;
f[1][1]=1; f[2][1]=2;
for(int i=3;i<=n;i++)
add(i);
for(int i=len;i>=1;i--)
cout<<f[n][i];
return 0;
}
```
by wang1h @ 2024-04-14 19:35:22
@[tlsonghangtong](/user/1056451)
by wang1h @ 2024-04-14 19:35:43
@[tlsonghangtong](/user/1056451)
```cpp
#include<bits/stdc++.h>
using namespace std;
#define maxn 2000
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 c){
return a[c];
}void flatten(int L){
len=L;
for(int c=1;c<=len;c++){
a[c+1]+=a[c]/10;a[c]%=10;
}for(;!a[len];)len--;
}void print(){
for(int c=max(len,1);c>=1;c--)cout<<a[c];
}
};Bigint operator+(Bigint a,Bigint b){
Bigint ans;
int len=max(a.len,b.len);
for(int c=1;c<=len;c++)ans[c]+=a[c]+b[c];
ans.flatten(len+1);
return ans;
}int main(){
int n;cin>>n;
Bigint f[5010];
f[1]=Bigint(1);
f[2]=Bigint(2);
for(int c=3;c<=n;c++)f[c]=f[c-1]+f[c-2];
f[n].print();
}
```
封装高精结构体
by xd244 @ 2024-04-14 19:42:30
@[xd244](/user/1153793)
@[wang1h](/user/556072)
已关，但能不能在我的代码上改？
by tlsonghangtong @ 2024-04-17 16:35:26
@[tlsonghangtong](/user/1056451) 好的:
```cpp
#include<bits/stdc++.h>
using namespace std;
#define maxn 2000
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 c){
return a[c];
}void flatten(int L){
len=L;
for(int c=1;c<=len;c++){
a[c+1]+=a[c]/10;a[c]%=10;
}for(;!a[len];)len--;
}void print(){
for(int c=max(len,1);c>=1;c--)cout<<a[c];
}
};
Bigint operator+(Bigint a,Bigint b){
Bigint ans;
int len=max(a.len,b.len);
for(int c=1;c<=len;c++)ans[c]+=a[c]+b[c];
ans.flatten(len+1);
return ans;
}
Bigint ans[5010];//记录答案
bool ansed[5010];//记录答案是否已经搜索过
Bigint f(int n){
if(n==1)return Bigint(1);
if(n==2)return Bigint(2);
if(n==3)return Bigint(4);
if(ansed[n]!=0)return ans[n];
return ans[n]=f(n-1)+f(n-2)+f(n-3);
}int main(){
int n;cin>>n;
f(n).print();
}
```
by xd244 @ 2024-04-17 20:30:01
@[xd244](/user/1153793)
谢谢
by tlsonghangtong @ 2024-04-21 08:56:52
@[xd244](/user/1153793) 高精度20分
by tlsonghangtong @ 2024-04-21 09:04:20
@[tlsonghangtong](/user/1056451) 其实我认为你用封装结构体不用写那麽多代码
况且我想问一下问什么要加f(n - 3)~~因为我看这道题是用斐波那契数列的~~
或许你可以这样写
```cpp
void add_CHY(int x,int y){
int max_len = max(edge[x].a_len,edge[y].a_len);
for(int j = 0;j < max_len;j++){
edge[i].a[j] += edge[x].a[j] + edge[y].a[j];
if(edge[i].a[j] > 9){
edge[i].a[j + 1]++;
edge[i].a[j] %= 10;
}
}
if(edge[i].a[max_len] != 0){
max_len++;
}
edge[i].a_len = max_len;
return;
}
```
~~不喜勿喷~~
by Before_Dream @ 2024-05-01 16:20:39