2020年5月5日 星期二

[LeetCode] 160. Intersection of Two Linked Lists* 解題思路 (Easy)



這題要找出兩個鏈結陣列相交的節點。




LeetCode 題目連結

 

https://leetcode.com/problems/intersection-of-two-linked-lists

 

題目

Write a program to find the node at which the intersection of two singly linked lists begins.
For example, the following two linked lists:

begin to intersect at node c1.

Example 1:

Input: intersectVal = 8, listA = [4,1,8,4,5], listB = [5,0,1,8,4,5], skipA = 2, skipB = 3
Output: Reference of the node with value = 8
Input Explanation: The intersected node's value is 8 (note that this must not be 0 if the two lists intersect). From the head of A, it reads as [4,1,8,4,5]. From the head of B, it reads as [5,0,1,8,4,5]. There are 2 nodes before the intersected node in A; There are 3 nodes before the intersected node in B.

Example 2:

Input: intersectVal = 2, listA = [0,9,1,2,4], listB = [3,2,4], skipA = 3, skipB = 1
Output: Reference of the node with value = 2
Input Explanation: The intersected node's value is 2 (note that this must not be 0 if the two lists intersect). From the head of A, it reads as [0,9,1,2,4]. From the head of B, it reads as [3,2,4]. There are 3 nodes before the intersected node in A; There are 1 node before the intersected node in B.

Example 3:

Input: intersectVal = 0, listA = [2,6,4], listB = [1,5], skipA = 3, skipB = 2
Output: null
Input Explanation: From the head of A, it reads as [2,6,4]. From the head of B, it reads as [1,5]. Since the two lists do not intersect, intersectVal must be 0, while skipA and skipB can be arbitrary values.
Explanation: The two lists do not intersect, so return null.

Accept 作法


這題時間複雜度為O(m+n)。


Runtime: 426 ms
Memory: 41.9 MB

Java 程式碼

public class Solution {
    public ListNode getIntersectionNode(ListNode headA, ListNode headB) {
        ListNode cur = headA;
        ListNode cur2 = headB;
        while(cur != cur2){
            cur = (cur!=null)? cur.next:headA;
            cur2 = (cur2!=null)? cur2.next:headB;
        }
        return cur;
        
    }
}

 

更多 LeetCode 相關資源

 

複習程式面試書籍


除了 LeetCode 練習外,我也入手了這本,題庫來自真正的面試,並非摘自教科書。它們反映出頂尖公司真正會出的題目,你可以藉此做好充分準備
需要的話可以看看,寫得很仔細。


書名:提升程式設計師的面試力:189道面試題目與解答



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