D.cpp

// #pragma GCC optimize("Ofast,unroll-loops")
// #pragma GCC target("avx,avx2,fma")

#include <bits/stdc++.h>
using namespace std;

#define ll long long
#define ull unsigned long long
#define dd double
#define ld long double
#define sl(n) scanf("%lld", &n)
#define si(n) scanf("%d", &n)
#define sd(n) scanf("%lf", &n)
#define pll pair <ll, ll>
#define pii pair <int, int>
#define mp make_pair
#define pb push_back
#define all(v) v.begin(), v.end()
#define inf (1LL << 61)
#define loop(i, start, stop, inc) for(ll i = start; i <= stop; i += inc)
#define for1(i, stop) for(ll i = 1; i <= stop; ++i)
#define for0(i, stop) for(ll i = 0; i < stop; ++i)
#define rep1(i, start) for(ll i = start; i >= 1; --i)
#define rep0(i, start) for(ll i = (start-1); i >= 0; --i)
#define ms(n, i) memset(n, i, sizeof(n))
#define casep(n) printf("Case %lld:", ++n)
#define pn printf("\n")
#define pf printf
#define EL '\n'
#define fastio std::ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);

// === DEBUG MACRO STARTS HERE === //
#ifndef ONLINE_JUDGE
#define DEBUG
#define SYS_COL system("COLOR")
#endif

int recur_depth = 0;
#ifdef DEBUG
#define dbg(x) {++recur_depth; auto x_=x; --recur_depth; SYS_COL; \
                cerr<<string(recur_depth, '\t')<<"\e[91m"<<__func__<<":" \
                <<__LINE__<<"\t"<<#x<<" = "<<x_<<"\e[39m"<<endl;}

template<typename Ostream, typename Cont>
typename enable_if<is_same<Ostream,ostream>::value,
            Ostream&>::type operator<<(Ostream& os,  const Cont& v) {
	os<<"[";
	for(auto& x:v){os<<x<<", ";}
	return os<<"]";
}
template<typename Ostream, typename ...Ts>
Ostream& operator<<(Ostream& os,  const pair<Ts...>& p){
	return os<<"{"<<p.first<<", "<<p.second<<"}";
}
#else
#define dbg(x)
#endif
// === DEBUG MACRO ENDS HERE === //

#define ff first
#define ss second

const ll sz = 2e5 + 10;
ll b[sz], ans[sz], done[sz], lft[sz];

int main()
{
    ll t;
    cin >> t;

    while(t--) {
        ll n, k = 0; sl(n);
        vector <int> lst;

        for1(i, n) {
            sl(b[i]);

            if(!done[ b[i] ]) {
                ans[i] = b[i];
                k++;
                done[ b[i] ] = 1;
                lft[ b[i] ] = i;
            }
        }

        for1(i, n) if(!done[i]) lst.pb(i);

        for1(i, n) {
            if(!ans[i]) {
                ll x = lst.back();

                if(x == i) {
                    ll l = lft[ b[i] ];
                    ans[l] = x, ans[i] = b[i];
                    lft[ b[i] ] = i;
                }
                else
                    ans[i] = x;

                lst.pop_back();
            }
        }

        pf("%lld\n", k);
        for1(i, n) pf("%lld ", ans[i]);
        pn;

        for1(i, n) ans[i] = done[i] = 0;
    }

    return 0;
}