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l203 remove linked list elements

admin 11月 13, 2020 0

题目描述

Remove all elements from a linked list of integers that have value val.

Example
Given: 1 --> 2 --> 6 --> 3 --> 4 --> 5 --> 6, val = 6
Return: 1 --> 2 --> 3 --> 4 --> 5

解题思路

使用prev指针记录当前节点的前一个节点，current表示当前节点
需要判断当前节点是否为head节点

Go实现

package main

import "fmt"

type ListNode struct {
    Val int
    Next *ListNode
}


func (head *ListNode,val int) *ListNode {
    if head == nil {
        head = new(ListNode)
        head.Val = val
    }else{
        tmp := head

        for tmp.Next!=nil {
            tmp = tmp.Next
        }
        node := new(ListNode)
        node.Val = val
        tmp.Next = node
    }
    return head
}

func removeElements(head *ListNode, val int) *ListNode {
    if head == nil{
        return nil
    }
    current:=head
    prev := head

    for current != nil {
        if current.Val == val {
            if current == head{
                prev = current.Next
                head = prev
            }else{
                prev.Next = current.Next
            }
        }else{
            prev = current
        }
        current = current.Next
    }
    return head
}

func printList(head *ListNode)  {
    for head != nil  {
        if head.Next!=nil {
            fmt.Printf("%d -> ", head.Val)
        }else{
            fmt.Println(head.Val)
        }
        head = head.Next
    }
}

func main(){
    
    //nums := []int{1,2}, val=1
    //nums := []int{1}, val=1
    //nums := []int{1,1}, val=1
    //nums :=[]int{1,2}, val=2
    nums := []int{1,2,2,1}
    var head *ListNode
    for _,v := range nums {
        head = insertNode(head, v)
    }
    printList(head)
    head=removeElements(head, 2)
    printList(head)
}