没辣么可怕，就是个斐波那契数列👀️ #include <stdio.h>

int main()

{

int n;

scanf("%d",&n);

int a[100];

a[0]=0;

a[1]=1;

a[2]=1;

a[3]=2;

for(int i=4;i<=n;i++){

a[i]=a[i-1]+a[i-2];

}

printf("%d\n",a[n]);

return 0;

}

#include<stdio.h>
int main(){
int n,a,t1=1,t=1;
scanf("%d",&a);
n=a-1;
int sum =1;
for(int i=1;i<=n/2;i++){
t1*=i;
t=1;
for(int j=n-i;j>n-i*2;j--){
t*=j;
}

t/=t1;

sum+=t;
}

printf("%d",sum);
return 0;
}

主打的就是理解

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


////递归超时 
//int dfs(int n){
//	if(n<=2)return n;
//	return dfs(n-1)+dfs(n-2);
//}


int main(){
	int n;
	cin>>n;
	if(n<=2)cout<<n;
	
	vector<int> arr(n+1);
	
	arr[1]=1;
	arr[2]=2;
	for(int i=3;i<=n;i++){
		arr[i]=arr[i-1]+arr[i-2];
	}
//	cout<<dfs(n-1);
	
	return 0;
}

#include<stdio.h>

int main(){

int n,a=1,b=1,c;

scanf("%d",&n);

for(int i=2;i<n;i++){

c=a;

a=a+b;

b=c; } printf("%d",a);

return 0; }

#include <cstring>
#include <stdio.h>
#include <algorithm>
int abc(int a)
{
if(a==1||a==2) return  1;
else return abc(a-1)+abc(a-2);
}
using namespace std;
int main()
{
int p;
cin>>p;
cout<<abc( p ) ;
}

斐波那契 注意已经在第一个台阶了！！！

n=int(input())
if n==2:
    print(1)
elif n==3:
    print(2)
else:
    a,b=1,2
    for i in range(4,n+1):
        a,b=b,a+b
    print(b)

//#include<bits/stdc++.h>
#define int long long
using namespace std;
int mem[100];
int dfs(int x)
{
	if(mem[x]) return mem[x];
	
	int sum = 0;
	if(x == 1) sum = 1;
	else if(x == 2) sum = 2;
	else sum = dfs (x - 1) + dfs(x - 2);
	
	mem[x] = sum;
	return sum;
}
signed main()
{
	int n;
	cin >> n;
	int res=dfs(n-1);
	cout << res << '\n';
	return 0;
//}

#include <stdio.h> int main() { int n; scanf("%d",&n); if(n1) { printf("1\n"); return 0; } if(n2) { printf("2\n"); return 0; } int a=1; int b=2; int current; for(int i = 3;i<=n;i++) { current=a+b; a=b; b=current; } printf("%d\n",a); return 0; }

#include <stdio.h>
#include "math.h"
int main()
{
    int count(int a, int b);
    int a,b=0,i=0;
    scanf("%d",&a);
    a=a-1;
    while (a-i>=a/2)
    {
        b+=count(a-i,i);
        i++;
    }
    printf("%d",b);
    return 0;
}
int count(int a, int b)
{
    int i,c=1;
    for(i=a;i>a-b;i--)
    {
        c*=i;
    }
    for(i=1;i<=b;i++)
    {
        c/=i;
    }
    return c;
}//函数计算排序数

#include<stdio.h> int main() { int n,f1=1,f2=2,sum; scanf("%d",&n); if(n1) printf("%d",n); else if(n1) printf("%d",n); else if(n==3) printf("2"); else {for(int i=4;i<=n;i++) { sum=f1+f2; f1=f2; f2=sum;} printf("%d",sum);} return 0; }

#include<stdio.h>
int main()
{
    int n;
    scanf("%d",&n);
    int num[30] = {0};
    num[1] = 1;
    num[2] = 1;
    for (int i = 3; i <= 25; i++) {
        num[i] = num[i-1]+num[i-2];
    }
    printf("%d",num[n]);
    return 0;
}