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IsListCyclic.java
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IsListCyclic.java
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package epi;
import epi.test_framework.EpiTest;
import epi.test_framework.GenericTest;
import epi.test_framework.TestFailure;
import epi.test_framework.TimedExecutor;
public class IsListCyclic {
public static ListNode<Integer> hasCycle(ListNode<Integer> head) {
// Implement this placeholder.
return null;
}
@EpiTest(testfile = "is_list_cyclic.tsv")
public static void HasCycleWrapper(TimedExecutor executor,
ListNode<Integer> head, int cycleIdx)
throws Exception {
int cycleLength = 0;
if (cycleIdx != -1) {
if (head == null) {
throw new RuntimeException("Can't cycle empty list");
}
ListNode<Integer> cycleStart = null, cursor = head;
while (cursor.next != null) {
if (cursor.data == cycleIdx) {
cycleStart = cursor;
}
cursor = cursor.next;
if (cycleStart != null) {
cycleLength++;
}
}
if (cursor.data == cycleIdx) {
cycleStart = cursor;
}
if (cycleStart == null) {
throw new RuntimeException("Can't find a cycle start");
}
cursor.next = cycleStart;
cycleLength++;
}
ListNode<Integer> result = executor.run(() -> hasCycle(head));
if (cycleIdx == -1) {
if (result != null) {
throw new TestFailure("Found a non-existing cycle");
}
} else {
if (result == null) {
throw new TestFailure("Existing cycle was not found");
}
ListNode<Integer> cursor = result;
do {
cursor = cursor.next;
cycleLength--;
if (cursor == null || cycleLength < 0) {
throw new TestFailure(
"Returned node does not belong to the cycle or is not the closest node to the head");
}
} while (cursor != result);
if (cycleLength != 0) {
throw new TestFailure(
"Returned node does not belong to the cycle or is not the closest node to the head");
}
}
}
public static void main(String[] args) {
System.exit(GenericTest
.runFromAnnotations(
args, new Object() {}.getClass().getEnclosingClass())
.ordinal());
}
}