package LeetCode_LinkedList;

/**
 * 題目：
 *      Write a program to find the node at which the intersection of two singly linked lists begins.
 *  解題思路：
 *      首先定義兩個nodeA,nodeB分別從連結串列A,連結串列B的頭部開始遍歷，當nodeA遍歷到A的末尾時，nodeA從連結串列B的頭部開始遍歷，
 *      當nodeB遍歷到連結串列B末尾時，nodeB從連結串列A的頭部開始遍歷，當nodeA和nodeB相等的時候，即為兩個連結串列交集的第一個節點。
 */
public class GetIntersectionNode_160_1017 {
    public ListNode GetIntersectionNode(ListNode headA, ListNode headB) {
        if (headA == null || headB == null) {
            return null;
        }

        ListNode nodeA = headA;
        ListNode nodeB = headB;

        while (nodeA != nodeB) {
            nodeA = nodeA == null ? headB : nodeA.next;//nodeA為空時，從連結串列B開始遍歷
            nodeB = nodeB == null ? headA : nodeB.next;//nodeB為空時，從連結串列A開始遍歷
        }
        return nodeA;
    }

    //主函式進行測試
    public static void main(String[] args) {
        ListNode node1 = new ListNode(1);
        ListNode node3 = new ListNode(3);
        ListNode node4 = new ListNode(5);
        ListNode node5 = new ListNode(7);
        ListNode node6 = new ListNode(9);
        ListNode node7 = new ListNode(11);

        node1.next = node3;
        node3.next = node4;
        node4.next = node5;
        node5.next = node6;
        node6.next = node7;

        ListNode node2 = new ListNode(2);
        ListNode node8 = new ListNode(4);

        node2.next = node8;
        node8.next = node6;

        GetIntersectionNode_160_1017 test = new GetIntersectionNode_160_1017();
        ListNode result = test.GetIntersectionNode(node1, node2);
            System.out.println(result.val);
    }
}