def solve():
    n = int(input())
    a = [tuple(map(int, input().split())) for i in range(n)]
 
    N = 2 * 10**5 + 5
    p = list(range(N))      
    size = [1] * N          
 
    def find(x):
        if x != p[x]:
            p[x] = find(p[x])  
        return p[x]
 
    def unite(x, y):
        x = find(x)
        y = find(y)
        if x == y:
            return False
 
        if size[x] < size[y]:
            x, y = y, x
        p[y] = x
        size[x] += size[y]
        return True
 
    s_indices = []
 
    for i in range(n):
        u, v = a[i]
        if unite(u, v):
            s_indices.append(i + 1)
 
    print(len(s_indices))
    print(*s_indices)
 
# Main
t = int(input())
for _ in range(t):
    solve()
 

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