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CourseSchedule.java
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CourseSchedule.java
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public class Solution {
public boolean canFinish(int numCourses, int[][] prerequisites) {
int[] incomes = new int[numCourses];
List<List<Integer>> adjs = new ArrayList<>();
initGraph(incomes, prerequisites, adjs);
Queue<Integer> queue = new LinkedList<>();
for (int i = 0; i < incomes.length; i++) {
if (incomes[i] == 0) queue.offer(i);
}
int visited = 0;
while (!queue.isEmpty()) {
int from = queue.poll();
visited++;
for (int to : adjs.get(from)) {
incomes[to]--;
if (incomes[to] == 0)
queue.offer(to);
}
}
return visited == numCourses;
}
private void initGraph(int[] incomes, int[][] prerequisites, List<List<Integer>> adjs) {
for (int i = 0; i < incomes.length; i++) {
adjs.add(new ArrayList<Integer>());
}
for (int[] pair : prerequisites) {
incomes[pair[0]]++;
adjs.get(pair[1]).add(pair[0]);
}
}
}