Minimum Time to Collect All Apples in a Tree LeetCode solution in Java

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class Solution {
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  public int minTime(int n, int[][] edges, List<Boolean> hasApple) {
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    HashMap<Integer, List<Integer>> graph = new HashMap<>(n);
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    for (int edge[] : edges) {
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      int a = edge[0], b = edge[1];
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      graph.putIfAbsent(a, new LinkedList<>());
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      graph.putIfAbsent(b, new LinkedList<>());
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      graph.get(a).add(b);
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      graph.get(b).add(a);
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    }
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    boolean[] visited = new boolean[n];
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    Arrays.fill(visited, false);
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    int a = move(0, graph, hasApple, n, visited);
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    return a == -1 ? 0 : a;
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  }
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  public int move(
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      int i,
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      HashMap<Integer, List<Integer>> graph,
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      List<Boolean> hasApple,
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      int n,
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      boolean[] visited) {
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    visited[i] = true;
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    boolean cont = false;
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    if (hasApple.get(i)) {
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      cont = true;
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    }
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    List<Integer> list = graph.get(i);
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    if (list == null) {
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      return cont ? 0 : -1;
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    }
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    int j = 0;
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    for (int k : list) {
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      if (!visited[k]) {
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        int a = move(k, graph, hasApple, n, visited);
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        if (a != -1) {
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          j += 2 + a;
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        }
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      }
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    }
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    if (j == 0 && cont) return 0;
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    return j == 0 ? -1 : j;
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  }
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}