#include <stdio.h>
 
#define N 200005
 
int c[N], size[N], vis[N], vid = 0;
 
int find(int x) {
    if (x != c[x])
        c[x] = find(c[x]);
    return c[x];
}
 
int unite(int x, int y) {
    x = find(x);
    y = find(y);
    if (x == y) return 0;
    if (size[x] < size[y]) {
        int temp = x;
        x = y;
        y = temp;
    }
    c[y] = x;
    size[x] += size[y];
    return 1;
}
 
void solve() {
    ++vid;
    int n;
    scanf("%d", &n);
    int s_indices[N], s_count = 0;
 
    for (int i = 0; i < n; ++i) {
        int u, v;
        scanf("%d %d", &u, &v);
 
        if (vis[u] != vid) {
            c[u] = u;
            size[u] = 1;
            vis[u] = vid;
        }
 
        if (vis[v] != vid) {
            c[v] = v;
            size[v] = 1;
            vis[v] = vid;
        }
 
        if (unite(u, v)) {
            s_indices[s_count++] = i + 1;
        }
    }
 
    printf("%d\n", s_count);
    for (int i = 0; i < s_count; ++i)
        printf("%d ", s_indices[i]);
    printf("\n");
}
 
int main() {
    int t;
    scanf("%d", &t);
    while (t--) solve();
    return 0;
}
 

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