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LeetCode 1462: Course Schedule IV Solution

Master LeetCode problem 1462 (Course Schedule IV), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

Problem Explanation

Explanation:

To solve this problem, we need to first build a directed graph representing the prerequisites of courses. Then, we can use a transitive closure algorithm to determine if one course is a prerequisite of another. Finally, we check each query against the transitive closure matrix to get the answers.

  1. Build a directed graph from the prerequisites array.
  2. Use Floyd-Warshall algorithm to calculate the transitive closure of the graph.
  3. Check each query against the transitive closure matrix to get the answers.

Time Complexity: O(n^3) where n is the number of courses.
Space Complexity: O(n^2) for the transitive closure matrix.

:

Solution Code

class Solution {
    public List<Boolean> checkIfPrerequisite(int numCourses, int[][] prerequisites, int[][] queries) {
        boolean[][] graph = new boolean[numCourses][numCourses];
        
        for (int[] pre : prerequisites) {
            graph[pre[0]][pre[1]] = true;
        }
        
        for (int k = 0; k < numCourses; k++) {
            for (int i = 0; i < numCourses; i++) {
                for (int j = 0; j < numCourses; j++) {
                    if (graph[i][k] && graph[k][j]) {
                        graph[i][j] = true;
                    }
                }
            }
        }
        
        List<Boolean> result = new ArrayList<>();
        for (int[] query : queries) {
            result.add(graph[query[0]][query[1]]);
        }
        
        return result;
    }
}

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