题解

#include <bits/stdc++.h>
using namespace std;
int main(){
    int a[1000005]={};
    int n,b;
    cin>>n;
    for(int i=1;i<=n;i++){
        cin>>a[i];
    }
    for(int i=1;i<=n;i+=2){
        b=a[i];
        a[i]=a[i+1];
        a[i+1]=b;
    }
    for(int i=1;i<=n;i++){
        cout<<a[i]<<" ";
    }
}

懒得写注释了