根据给定值对链表进行分区，并保持原始顺序
给定一个链表和一个值x，对它进行分区，以使所有小于x的节点排在最前面，然后是所有值等于x的节点，最后是值大于或等于x的节点。 三个分区中每个分区中节点的原始相对顺序都应保留。 分区必须原地工作。
例子：
Input : 1->4->3->2->5->2->3,
x = 3
Output: 1->2->2->3->3->4->5
Input : 1->4->2->10
x = 3
Output: 1->2->4->10
Input : 10->4->20->10->3
x = 3
Output: 3->10->4->20->10
为了解决此问题，我们可以使用快速排序的分区方法，但这不会保留两个分区中每个分区中节点的原始相对顺序。
以下是解决此问题的算法：
-
将以下三个链表的第一个和最后一个节点初始化为
NULL。-
小于
x的值的链表。 -
等于
x的值的链表。 -
大于
x的值的链表。
-
-
现在遍历原始链表。 如果节点的值小于
x，则将其附加在较小列表的末尾。 如果值等于x，则在等于列表的末尾。 如果值更大，则在更大列表的末尾。 -
现在连接三个列表。
以下是上述想法的实现。
C++
// C++ program to partition a linked list around a
// given value.
#include<bits/stdc++.h>
using namespace std;
/* Link list Node */
struct Node
{
int data;
struct Node* next;
};
// A utility function to create a new node
Node *newNode(int data)
{
struct Node* new_node = new Node;
new_node->data = data;
new_node->next = NULL;
return new_node;
}
// Function to make two separate lists and return
// head after concatinating
struct Node *partition(struct Node *head, int x)
{
/* Let us initialize first and last nodes of
three linked lists
1) Linked list of values smaller than x.
2) Linked list of values equal to x.
3) Linked list of values greater than x.*/
struct Node *smallerHead = NULL, *smallerLast = NULL;
struct Node *greaterLast = NULL, *greaterHead = NULL;
struct Node *equalHead = NULL, *equalLast = NULL;
// Now iterate original list and connect nodes
// of appropriate linked lists.
while (head != NULL)
{
// If current node is equal to x, append it
// to the list of x values
if (head->data == x)
{
if (equalHead == NULL)
equalHead = equalLast = head;
else
{
equalLast->next = head;
equalLast = equalLast->next;
}
}
// If current node is less than X, append
// it to the list of smaller values
else if (head->data < x)
{
if (smallerHead == NULL)
smallerLast = smallerHead = head;
else
{
smallerLast->next = head;
smallerLast = head;
}
}
else // Append to the list of greater values
{
if (greaterHead == NULL)
greaterLast = greaterHead = head;
else
{
greaterLast->next = head;
greaterLast = head;
}
}
head = head->next;
}
// Fix end of greater linked list to NULL if this
// list has some nodes
if (greaterLast != NULL)
greaterLast->next = NULL;
// Connect three lists
// If smaller list is empty
if (smallerHead == NULL)
{
if (equalHead == NULL)
return greaterHead;
equalLast->next = greaterHead;
return equalHead;
}
// If smaller list is not empty
// and equal list is empty
if (equalHead == NULL)
{
smallerLast->next = greaterHead;
return smallerHead;
}
// If both smaller and equal list
// are non-empty
smallerLast->next = equalHead;
equalLast->next = greaterHead;
return smallerHead;
}
/* Function to print linked list */
void printList(struct Node *head)
{
struct Node *temp = head;
while (temp != NULL)
{
printf("%d ", temp->data);
temp = temp->next;
}
}
// Driver program to run the case
int main()
{
/* Start with the empty list */
struct Node* head = newNode(10);
head->next = newNode(4);
head->next->next = newNode(5);
head->next->next->next = newNode(30);
head->next->next->next->next = newNode(2);
head->next->next->next->next->next = newNode(50);
int x = 3;
head = partition(head, x);
printList(head);
return 0;
}
Java
// Java program to partition a
// linked list around a given value.
class GfG
{
/* Link list Node */
static class Node
{
int data;
Node next;
}
// A utility function to create a new node
static Node newNode(int data)
{
Node new_node = new Node();
new_node.data = data;
new_node.next = null;
return new_node;
}
// Function to make two separate lists and return
// head after concatinating
static Node partition(Node head, int x)
{
/* Let us initialize first and last nodes of
three linked lists
1) Linked list of values smaller than x.
2) Linked list of values equal to x.
3) Linked list of values greater than x.*/
Node smallerHead = null, smallerLast = null;
Node greaterLast = null, greaterHead = null;
Node equalHead = null, equalLast =null;
// Now iterate original list and connect nodes
// of appropriate linked lists.
while (head != null)
{
// If current node is equal to x, append it
// to the list of x values
if (head.data == x)
{
if (equalHead == null)
equalHead = equalLast = head;
else
{
equalLast.next = head;
equalLast = equalLast.next;
}
}
// If current node is less than X, append
// it to the list of smaller values
else if (head.data < x)
{
if (smallerHead == null)
smallerLast = smallerHead = head;
else
{
smallerLast.next = head;
smallerLast = head;
}
}
else // Append to the list of greater values
{
if (greaterHead == null)
greaterLast = greaterHead = head;
else
{
greaterLast.next = head;
greaterLast = head;
}
}
head = head.next;
}
// Fix end of greater linked list to NULL if this
// list has some nodes
if (greaterLast != null)
greaterLast.next = null;
// Connect three lists
// If smaller list is empty
if (smallerHead == null)
{
if (equalHead == null)
return greaterHead;
equalLast.next = greaterHead;
return equalHead;
}
// If smaller list is not empty
// and equal list is empty
if (equalHead == null)
{
smallerLast.next = greaterHead;
return smallerHead;
}
// If both smaller and equal list
// are non-empty
smallerLast.next = equalHead;
equalLast.next = greaterHead;
return smallerHead;
}
/* Function to print linked list */
static void printList(Node head)
{
Node temp = head;
while (temp != null)
{
System.out.print(temp.data + " ");
temp = temp.next;
}
}
// Driver code
public static void main(String[] args)
{
/* Start with the empty list */
Node head = newNode(10);
head.next = newNode(4);
head.next.next = newNode(5);
head.next.next.next = newNode(30);
head.next.next.next.next = newNode(2);
head.next.next.next.next.next = newNode(50);
int x = 3;
head = partition(head, x);
printList(head);
}
}
// This code is contributed by Prerna saini.
Python3
# Python3 program to partition a
# linked list around a given value.
# Link list Node
class Node:
def __init__(self):
self.data = 0
self.next = None
# A utility function to create a new node
def newNode( data):
new_node = Node()
new_node.data = data
new_node.next = None
return new_node
# Function to make two separate lists and return
# head after concatinating
def partition( head, x) :
# Let us initialize first and last nodes of
# three linked lists
# 1) Linked list of values smaller than x.
# 2) Linked list of values equal to x.
# 3) Linked list of values greater than x.
smallerHead = None
smallerLast = None
greaterLast = None
greaterHead = None
equalHead = None
equalLast = None
# Now iterate original list and connect nodes
# of appropriate linked lists.
while (head != None) :
# If current node is equal to x, append it
# to the list of x values
if (head.data == x):
if (equalHead == None):
equalHead = equalLast = head
else:
equalLast.next = head
equalLast = equalLast.next
# If current node is less than X, append
# it to the list of smaller values
elif (head.data < x):
if (smallerHead == None):
smallerLast = smallerHead = head
else:
smallerLast.next = head
smallerLast = head
else :
# Append to the list of greater values
if (greaterHead == None) :
greaterLast = greaterHead = head
else:
greaterLast.next = head
greaterLast = head
head = head.next
# Fix end of greater linked list to None if this
# list has some nodes
if (greaterLast != None) :
greaterLast.next = None
# Connect three lists
# If smaller list is empty
if (smallerHead == None) :
if (equalHead == None) :
return greaterHead
equalLast.next = greaterHead
return equalHead
# If smaller list is not empty
# and equal list is empty
if (equalHead == None) :
smallerLast.next = greaterHead
return smallerHead
# If both smaller and equal list
# are non-empty
smallerLast.next = equalHead
equalLast.next = greaterHead
return smallerHead
# Function to print linked list
def printList(head) :
temp = head
while (temp != None):
print(temp.data ,end= " ")
temp = temp.next
# Driver code
# Start with the empty list
head = newNode(10)
head.next = newNode(4)
head.next.next = newNode(5)
head.next.next.next = newNode(30)
head.next.next.next.next = newNode(2)
head.next.next.next.next.next = newNode(50)
x = 3
head = partition(head, x)
printList(head)
# This code is contributed by Arnab Kundu.
C
// C# program to partition a
// linked list around a given value.
using System;
public class GfG
{
/* Link list Node */
public class Node
{
public int data;
public Node next;
}
// A utility function to create a new node
static Node newNode(int data)
{
Node new_node = new Node();
new_node.data = data;
new_node.next = null;
return new_node;
}
// Function to make two separate lists and return
// head after concatinating
static Node partition(Node head, int x)
{
/* Let us initialize first and last nodes of
three linked lists
1) Linked list of values smaller than x.
2) Linked list of values equal to x.
3) Linked list of values greater than x.*/
Node smallerHead = null, smallerLast = null;
Node greaterLast = null, greaterHead = null;
Node equalHead = null, equalLast =null;
// Now iterate original list and connect nodes
// of appropriate linked lists.
while (head != null)
{
// If current node is equal to x, append it
// to the list of x values
if (head.data == x)
{
if (equalHead == null)
equalHead = equalLast = head;
else
{
equalLast.next = head;
equalLast = equalLast.next;
}
}
// If current node is less than X, append
// it to the list of smaller values
else if (head.data < x)
{
if (smallerHead == null)
smallerLast = smallerHead = head;
else
{
smallerLast.next = head;
smallerLast = head;
}
}
else // Append to the list of greater values
{
if (greaterHead == null)
greaterLast = greaterHead = head;
else
{
greaterLast.next = head;
greaterLast = head;
}
}
head = head.next;
}
// Fix end of greater linked list to NULL if this
// list has some nodes
if (greaterLast != null)
greaterLast.next = null;
// Connect three lists
// If smaller list is empty
if (smallerHead == null)
{
if (equalHead == null)
return greaterHead;
equalLast.next = greaterHead;
return equalHead;
}
// If smaller list is not empty
// and equal list is empty
if (equalHead == null)
{
smallerLast.next = greaterHead;
return smallerHead;
}
// If both smaller and equal list
// are non-empty
smallerLast.next = equalHead;
equalLast.next = greaterHead;
return smallerHead;
}
/* Function to print linked list */
static void printList(Node head)
{
Node temp = head;
while (temp != null)
{
Console.Write(temp.data + " ");
temp = temp.next;
}
}
// Driver code
public static void Main()
{
/* Start with the empty list */
Node head = newNode(10);
head.next = newNode(4);
head.next.next = newNode(5);
head.next.next.next = newNode(30);
head.next.next.next.next = newNode(2);
head.next.next.next.next.next = newNode(50);
int x = 3;
head = partition(head, x);
printList(head);
}
}
/* This code contributed by PrinciRaj1992 */
输出：
2 10 4 5 30 50
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