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34 lines (31 loc) · 946 Bytes
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a_141.java
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34 lines (31 loc) · 946 Bytes
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package doublepointer;
public class a_141 {
/*public boolean hasCycle(ListNode head) {
if (head == null) return false;
ListNode i = head, j = head.next;
while(j != null) {
if (i == j) return true;
j = j.next;
}
return false;
}*/ //错误解法
//双指针,一个指针每次移动一个节点，一个指针每次移动二个节点，如果存在环，那么这两个指针一定会相遇。
public boolean hasCycle(ListNode head) {
if (head == null) return false;
ListNode i = head, j = head.next;
while (i != null && j != null && j.next != null) {
if (i == j) return true;
i = i.next;
j = j.next.next;
}
return false;
}
class ListNode {
int val;
ListNode next;
ListNode(int x) {
val = x;
next = null;
}
}
}