#include<iostream>
#include<queue>
#include<cstdio>
#include<cstring>
#include<string>
#include<algorithm>
#include<vector>
#include<functional>
#define MAX_N 100005
using namespace std;

struct node {
public:
    int val;
    int pos;

    node(int v, int p) : val(v), pos(p) { }

    node() { }

    bool operator<(const node &a) const {
        return val > a.val;
    }
};

priority_queue<node> que;

int n;
int T;

vector<node> L[MAX_N];
vector<int> G;
int l[MAX_N],r[MAX_N];

bool used[MAX_N];

void init() {
    for (int i = 0; i <= n; i++)L[i].clear();
    memset(used,0,sizeof(used));
    G.clear();
    while (que.size())que.pop();
}

int main() {
    scanf("%d", &T);
    while (T--) {
        scanf("%d", &n);
        init();
        for (int i = 0; i < n; i++)
            scanf("%d", &l[i]);
        for (int i = 0; i < n; i++)
            scanf("%d", &r[i]);
        for (int i = 0; i < n; i++)
            L[l[i]].push_back(node(r[i], i + 1));
        int ans = 0;
        for (int i = 0; i <= n; i++) {
            for (int j = 0; j < L[i].size(); j++)que.push(L[i][j]);
            while (que.size() && que.top().val < i)que.pop();
            if (que.empty()) {
                ans = i;
                break;
            }
            G.push_back(que.top().pos);
            que.pop();
        }
        printf("%d\n", ans);
        for (int i = 0; i < G.size(); i++) {
            printf("%d ", G[i]);
            used[G[i]] = 1;
        }
        for (int i = 1; i <= n; i++)if (!used[i])printf("%d ", i);
        printf("\n");

    }
    return 0;
}