void solve() { int n ; cin >> n; string s ; cin >> s; vector check(n); for (int i = 0 ; i < n ; i++) check[i] = (s[i] == '1'); vectora(n); input(a); vectorindegree(n); for (int i = 0 ; i < n ; i++) { indegree[--a[i]]++; } queue q; vector ans; for (int i = 0 ; i < n ; i++) { if (indegree[i] == 0)q.push(i); } while (!q.empty()) { int u = q.front(); q.pop(); if (check[u]) { ans.push_back(u); check[u] = !check[u]; check[a[u]] = !check[a[u]]; } indegree[a[u]]--; if (indegree[a[u]] == 0)q.push(a[u]); } for (int i = 0 ; i < n ; i++) { if (indegree[i]) { int j = i; int length = 0 , track = 0 , res = 0; while (indegree[j]) { if (check[j]) track ^= 1; res += track; indegree[j] = 0; length++; j = a[j]; } if (track == 1) { cout << -1 << endl; return; } for (int k = 0 ; k < length ; k++) { if (check[j]) track ^= 1; if (track == (res < length — res)) { ans.push_back(j); } j = a[j]; } } } cout << ans.size() << endl; for (auto a : ans) cout << a + 1 << " "; cout << endl; }