Course Schedule IV LeetCode solution in Java

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class Solution {
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  public List<Boolean> checkIfPrerequisite(int numCourses, int[][] prerequisites, int[][] queries) {
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    // Generating Map
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    Map<Integer, List<Integer>> graph = new HashMap<>();
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    for (int e[] : prerequisites) {
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      graph.putIfAbsent(e[0], new ArrayList<>());
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      graph.get(e[0]).add(e[1]);
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    }
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    List<Boolean> list = new ArrayList<>();
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    // Appling DFS for every query to get result
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    for (int[] q : queries) {
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      list.add(isPre(q[0], q[1], graph, new HashSet<>()));
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    }
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    return list;
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  }
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  // Check if src comes before dst using DFS
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  private boolean isPre(int src, int dst, Map<Integer, List<Integer>> adj, Set<Integer> visited) {
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    if (visited.contains(src)) return false;
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    visited.add(src);
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    for (int neigh : adj.getOrDefault(src, new ArrayList<>())) {
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      if (neigh == dst || isPre(neigh, dst, adj, visited)) return true;
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    }
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    return false;
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  }
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}