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Commit 612315d

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Merge pull request youngyangyang04#1311 from wzqwtt/patch03
添加(0707.设计链表、0206.翻转链表、0024.两两交换链表中的节点)Scala版本
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‎problems/0024.两两交换链表中的节点.md

Lines changed: 23 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -311,7 +311,29 @@ func swapPairs(_ head: ListNode?) -> ListNode? {
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return dummyHead.next
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}
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```
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Scala:
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```scala
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// 虚拟头节点
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object Solution {
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def swapPairs(head: ListNode): ListNode = {
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var dummy = new ListNode(0, head) // 虚拟头节点
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var pre = dummy
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var cur = head
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// 当pre的下一个和下下个都不为空,才进行两两转换
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while (pre.next != null && pre.next.next != null) {
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var tmp: ListNode = cur.next.next // 缓存下一次要进行转换的第一个节点
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pre.next = cur.next // 步骤一
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cur.next.next = cur // 步骤二
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cur.next = tmp // 步骤三
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// 下面是准备下一轮的交换
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pre = cur
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cur = tmp
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}
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// 最终返回dummy虚拟头节点的下一个,return可以省略
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dummy.next
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}
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}
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```
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<div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>

‎problems/0206.翻转链表.md

Lines changed: 34 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -496,6 +496,40 @@ struct ListNode* reverseList(struct ListNode* head){
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return reverse(NULL, head);
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}
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```
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Scala:
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双指针法:
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```scala
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object Solution {
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def reverseList(head: ListNode): ListNode = {
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var pre: ListNode = null
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var cur = head
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while (cur != null) {
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var tmp = cur.next
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cur.next = pre
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pre = cur
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cur = tmp
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}
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pre
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}
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}
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```
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递归法:
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```scala
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object Solution {
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def reverseList(head: ListNode): ListNode = {
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reverse(null, head)
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}
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def reverse(pre: ListNode, cur: ListNode): ListNode = {
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if (cur == null) {
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return pre // 如果当前cur为空,则返回pre
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}
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val tmp: ListNode = cur.next
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cur.next = pre
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reverse(cur, tmp) // 此时cur成为前一个节点,tmp是当前节点
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}
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}
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```
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-----------------------
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<div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>

‎problems/0707.设计链表.md

Lines changed: 68 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1154,7 +1154,75 @@ class MyLinkedList {
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}
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```
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Scala:
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```scala
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class ListNode(_x: Int = 0, _next: ListNode = null) {
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var next: ListNode = _next
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var x: Int = _x
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}
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class MyLinkedList() {
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var size = 0 // 链表尺寸
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var dummy: ListNode = new ListNode(0) // 虚拟头节点
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// 获取第index个节点的值
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def get(index: Int): Int = {
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if (index < 0 || index >= size) {
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return -1;
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}
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var cur = dummy
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for (i <- 0 to index) {
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cur = cur.next
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}
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cur.x // 返回cur的值
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}
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// 在链表最前面插入一个节点
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def addAtHead(`val`: Int) {
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addAtIndex(0, `val`)
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}
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// 在链表最后面插入一个节点
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def addAtTail(`val`: Int) {
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addAtIndex(size, `val`)
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}
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// 在第index个节点之前插入一个新节点
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// 如果index等于链表长度,则说明新插入的节点是尾巴
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// 如果index等于0,则说明新插入的节点是头
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// 如果index>链表长度,则说明为空
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def addAtIndex(index: Int, `val`: Int) {
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if (index > size) {
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return
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}
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var loc = index // 因为参数index是val不可变类型,所以需要赋值给一个可变类型
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if (index < 0) {
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loc = 0
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}
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size += 1 //链表尺寸+1
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var pre = dummy
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for (i <- 0 until loc) {
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pre = pre.next
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}
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val node: ListNode = new ListNode(`val`, pre.next)
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pre.next = node
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}
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// 删除第index个节点
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def deleteAtIndex(index: Int) {
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if (index < 0 || index >= size) {
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return
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}
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size -= 1
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var pre = dummy
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for (i <- 0 until index) {
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pre = pre.next
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}
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pre.next = pre.next.next
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}
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}
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```
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