题解 | 小红的排列构造①

#include<bits/stdc++.h>
using namespace std;
int main(){
    int n;
    cin >> n;
    vector<int> arr(n+1);
    if(n<=2) {
        cout << "-1";
        return 0;
    }
    for(int i=1; i<=n ;i++){
        if(n%2==0){
            if(i%2==1) arr[i] = n-i;
        if(i%2==0) arr[i] = n-i+2;
        }else {
            arr[i] = n-i+1;
        }
    }
    for(int i=1; i<=n; i++){
        cout << arr[i] << " ";
    }
}

控制永远是偶数就行了