TIOJ 1020 F.Number Insertion

#include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <vector>
using namespace std;
int n;
int num;
vector<int> v, ans;
bool compare(){
    for (int i = 0; i < n+1; ++i){
        if(v[i] != ans[i])
            return v[i] > ans[i];
    }
    return false;
}

void dfs(int x){
    if (x > n){
        if(compare())
            ans = v;
        num++;
        return;
    }
    for(int i = 1; i < x ;++i){
        if( x % (v[i-1] + v[i]) == 0 ){
            v.insert(v.begin()+i, x);
            dfs(x+1);
            v.erase(v.begin()+i);
        }
    }
}
int main(){
    scanf("%d",&n);
    v.push_back(0);
    v.push_back(1);
    num = 0;
    for (int i = 0; i <= n; ++i)
        ans.push_back(0);
    dfs(2);
    printf("%d\n",num);
    for (int i = 0; i < n; ++i){
        printf("%d ",ans[i]);
    }
    printf("%d\n",ans[n]);
}