658D.cpp

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*/                              
#include<bits/stdc++.h>
using namespace std;
 
#define fastio ios_base::sync_with_stdio(0); cin.tie(0)
#define LL long long 
#define mod 1000000007 
#define FOR(i, j, k) for (auto i=j ; i<k ; i++)
#define ROF(i, j, k) for (auto i=j ; i>=k ; i--) 
#define debug(...) fprintf(stderr, __VA_ARGS__), fflush(stderr)
#define time__(d) for(long blockTime = 0; (blockTime == 0 ? (blockTime=clock()) != 0 : false); debug("%s time : %.4fs", d, (double)(clock() - blockTime) / CLOCKS_PER_SEC))

const long long INF = 1e18;
const long long MAX = 1e5+10;
int main(){
    fastio;
    int t=1; cin>>t;
    while(t--){
        int n; cin>>n;  string A ,B; cin>>A>>B;
        vector<int>p; 
        int l=0,rev=0,cnt=0;
        ROF(i,n-1,0){
            int a,b=B[i]-'0';
            if(rev) {
                a=A[l-i]-'0';
                a=(cnt%2)^a;
                if(a==b) continue;
                int c=A[0]-'0';
                if(c==a) p.push_back(i+1);
                else p.push_back(1),p.push_back(i+1);
            }else {
              
            } 
        }
        cout<<p.size()<<" ";
        FOR(i,0,p.size()) cout<<p[i]<<" ";
        cout<<"\n";
    }
}