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Merge pull request youngyangyang04#1312 from wzqwtt/pacth04

添加(0019.删除链表的倒数第N个节点、面试题02.07.链表相交)Scala版本

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problems
- 0019.删除链表的倒数第N个节点.md
- 面试题02.07.链表相交.md

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`‎problems/0019.删除链表的倒数第N个节点.md`

Lines changed: 23 additions & 1 deletion

Original file line number	Diff line number	Diff line change
`@@ -289,6 +289,28 @@ func removeNthFromEnd(_ head: ListNode?, _ n: Int) -> ListNode? {`
`289`	`289`	`return dummyHead.next`
`290`	`290`	`}`
`291`	`291`	```
`292`		`-`
	`292`	`+Scala:`
	`293`	+```scala
	`294`	`+object Solution {`
	`295`	`+ def removeNthFromEnd(head: ListNode, n: Int): ListNode = {`
	`296`	`+ val dummy = new ListNode(-1, head) // 定义虚拟头节点`
	`297`	`+ var fast = head // 快指针从头开始走`
	`298`	`+ var slow = dummy // 慢指针从虚拟头开始头`
	`299`	`+ // 因为参数 n 是不可变量,所以不能使用 while(n>0){n-=1}的方式`
	`300`	`+ for (i <- 0 until n) {`
	`301`	`+ fast = fast.next`
	`302`	`+ }`
	`303`	`+ // 快指针和满指针一起走,直到fast走到null`
	`304`	`+ while (fast != null) {`
	`305`	`+ slow = slow.next`
	`306`	`+ fast = fast.next`
	`307`	`+ }`
	`308`	`+ // 删除slow的下一个节点`
	`309`	`+ slow.next = slow.next.next`
	`310`	`+ // 返回虚拟头节点的下一个`
	`311`	`+ dummy.next`
	`312`	`+ }`
	`313`	`+}`
	`314`	+```
`293`	`315`	`-----------------------`
`294`	`316`	`<div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>`

`‎problems/面试题02.07.链表相交.md`

Lines changed: 49 additions & 1 deletion

Original file line number	Diff line number	Diff line change
`@@ -317,7 +317,55 @@ ListNode getIntersectionNode(ListNode headA, ListNode *headB) {`
`317`	`317`	`}`
`318`	`318`	```
`319`	`319`
`320`		`-`
	`320`	`+Scala:`
	`321`	+```scala
	`322`	`+object Solution {`
	`323`	`+ def getIntersectionNode(headA: ListNode, headB: ListNode): ListNode = {`
	`324`	`+ var lenA = 0 // headA链表的长度`
	`325`	`+ var lenB = 0 // headB链表的长度`
	`326`	`+ var tmp = headA // 临时变量`
	`327`	`+ // 统计headA的长度`
	`328`	`+ while (tmp != null) {`
	`329`	`+ lenA += 1;`
	`330`	`+ tmp = tmp.next`
	`331`	`+ }`
	`332`	`+ // 统计headB的长度`
	`333`	`+ tmp = headB // 临时变量赋值给headB`
	`334`	`+ while (tmp != null) {`
	`335`	`+ lenB += 1`
	`336`	`+ tmp = tmp.next`
	`337`	`+ }`
	`338`	`+ // 因为传递过来的参数是不可变量,所以需要重新定义`
	`339`	`+ var listA = headA`
	`340`	`+ var listB = headB`
	`341`	`+ // 两个链表的长度差`
	`342`	`+ // 如果gap>0,lenA>lenB,headA(listA)链表往前移动gap步`
	`343`	`+ // 如果gap<0,lenA<lenB,headB(listB)链表往前移动-gap步`
	`344`	`+ var gap = lenA - lenB`
	`345`	`+ if (gap > 0) {`
	`346`	`+ // 因为不可以i-=1,所以可以使用for`
	`347`	`+ for (i <- 0 until gap) {`
	`348`	`+ listA = listA.next // 链表headA(listA) 移动`
	`349`	`+ }`
	`350`	`+ } else {`
	`351`	`+ gap = math.abs(gap) // 此刻gap为负值,取绝对值`
	`352`	`+ for (i <- 0 until gap) {`
	`353`	`+ listB = listB.next`
	`354`	`+ }`
	`355`	`+ }`
	`356`	`+ // 现在两个链表同时往前走,如果相等则返回`
	`357`	`+ while (listA != null && listB != null) {`
	`358`	`+ if (listA == listB) {`
	`359`	`+ return listA`
	`360`	`+ }`
	`361`	`+ listA = listA.next`
	`362`	`+ listB = listB.next`
	`363`	`+ }`
	`364`	`+ // 如果链表没有相交则返回null,return可以省略`
	`365`	`+ null`
	`366`	`+ }`
	`367`	`+}`
	`368`	+```
`321`	`369`
`322`	`370`
`323`	`371`	`-----------------------`

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`‎problems/0019.删除链表的倒数第N个节点.md`

`‎problems/面试题02.07.链表相交.md`

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