搜索链表中的元素（迭代和递归）

编写一个函数，在给定的单向链表中搜索给定的键“x”。如果 x 存在于链表中，则该函数应返回 true，否则返回 false。

bool search(Node *head, int x) 

例如，如果要搜索的键是 15，链表是 14->21->11->30->10，那么函数应该返回 false。如果要搜索的键是 14，则该函数应返回 true。
迭代解决方案

1) Initialize a node pointer, current = head.
2) Do following while current is not NULL
    a) current->key is equal to the key being searched return true.
    b) current = current->next
3) Return false 

以下是上述算法的迭代实现以搜索给定的键。

C++

// Iterative C++ program to search 
// an element in linked list 
#include 
using namespace std; 
  
/* Link list node */
class Node 
{ 
    public:
    int key; 
    Node* next; 
}; 
  
/* Given a reference (pointer to pointer) to the head 
of a list and an int, push a new node on the front 
of the list. */
void push(Node** head_ref, int new_key) 
{ 
    /* allocate node */
    Node* new_node = new Node();
  
    /* put in the key */
    new_node->key = new_key; 
  
    /* link the old list off the new node */
    new_node->next = (*head_ref); 
  
    /* move the head to point to the new node */
    (*head_ref) = new_node; 
} 
  
/* Checks whether the value x is present in linked list */
bool search(Node* head, int x) 
{ 
    Node* current = head; // Initialize current 
    while (current != NULL) 
    { 
        if (current->key == x) 
            return true; 
        current = current->next; 
    } 
    return false; 
} 
  
/* Driver program to test count function*/
int main() 
{ 
    /* Start with the empty list */
    Node* head = NULL; 
    int x = 21; 
  
    /* Use push() to construct below list 
    14->21->11->30->10 */
    push(&head, 10); 
    push(&head, 30); 
    push(&head, 11); 
    push(&head, 21); 
    push(&head, 14); 
  
    search(head, 21)? cout<<"Yes" : cout<<"No"; 
    return 0; 
} 
  
// This is code is contributed by rathbhupendra

C

// Iterative C program to search an element in linked list
#include
#include
#include
  
/* Link list node */
struct Node
{
    int key;
    struct Node* next;
};
  
/* Given a reference (pointer to pointer) to the head
  of a list and an int, push a new node on the front
  of the list. */
void push(struct Node** head_ref, int new_key)
{
    /* allocate node */
    struct Node* new_node =
            (struct Node*) malloc(sizeof(struct Node));
  
    /* put in the key  */
    new_node->key  = new_key;
  
    /* link the old list off the new node */
    new_node->next = (*head_ref);
  
    /* move the head to point to the new node */
    (*head_ref)    = new_node;
}
  
/* Checks whether the value x is present in linked list */
bool search(struct Node* head, int x)
{
    struct Node* current = head;  // Initialize current
    while (current != NULL)
    {
        if (current->key == x)
            return true;
        current = current->next;
    }
    return false;
}
  
/* Driver program to test count function*/
int main()
{
    /* Start with the empty list */
    struct Node* head = NULL;
    int x = 21;
  
    /* Use push() to construct below list
     14->21->11->30->10  */
    push(&head, 10);
    push(&head, 30);
    push(&head, 11);
    push(&head, 21);
    push(&head, 14);
  
    search(head, 21)? printf("Yes") : printf("No");
    return 0;
}

Java

// Iterative Java program to search an element
// in linked list
  
//Node class
class Node
{
    int data;
    Node next;
    Node(int d)
    {
        data = d;
        next = null;
    }
}
  
//Linked list class
class LinkedList
{
    Node head;    //Head of list
  
    //Inserts a new node at the front of the list
    public void push(int new_data)
    {
        //Allocate new node and putting data
        Node new_node = new Node(new_data);
  
        //Make next of new node as head
        new_node.next = head;
  
        //Move the head to point to new Node
        head = new_node;
    }
  
    //Checks whether the value x is present in linked list
    public boolean search(Node head, int x)
    {
        Node current = head;    //Initialize current
        while (current != null)
        {
            if (current.data == x)
                return true;    //data found
            current = current.next;
        }
        return false;    //data not found
    }
  
    //Driver function to test the above functions
    public static void main(String args[])
    {
  
        //Start with the empty list
        LinkedList llist = new LinkedList();
  
        /*Use push() to construct below list
        14->21->11->30->10  */
        llist.push(10);
        llist.push(30);
        llist.push(11);
        llist.push(21);
        llist.push(14);
  
        if (llist.search(llist.head, 21))
            System.out.println("Yes");
        else
            System.out.println("No");
    }
}
// This code is contributed by Pratik Agarwal

Python

# Iterative Python program to search an element
# in linked list
  
# Node class
class Node:
      
    # Function to initialise the node object
    def __init__(self, data):
        self.data = data # Assign data
        self.next = None # Initialize next as null
  
# Linked List class
class LinkedList:
    def __init__(self):
        self.head = None # Initialize head as None
  
    # This function insert a new node at the
    # beginning of the linked list
    def push(self, new_data):
      
        # Create a new Node
        new_node = Node(new_data)
  
        # 3. Make next of new Node as head
        new_node.next = self.head
  
        # 4. Move the head to point to new Node
        self.head = new_node
  
    # This Function checks whether the value
    # x present in the linked list 
    def search(self, x):
  
        # Initialize current to head
        current = self.head
  
        # loop till current not equal to None
        while current != None:
            if current.data == x:
                return True # data found
              
            current = current.next
          
        return False # Data Not found
  
  
# Code execution starts here
if __name__ == '__main__':
  
    # Start with the empty list
    llist = LinkedList()
  
    ''' Use push() to construct below list
        14->21->11->30->10 '''
    llist.push(10);
    llist.push(30);
    llist.push(11);
    llist.push(21);
    llist.push(14);
  
    if llist.search(21):
        print("Yes")
    else:
        print("No")
  
# This code is contributed by Ravi Shankar

C#

// Iterative C# program to search an element
// in linked list
using System;
  
// Node class
public class Node
{
    public int data;
    public Node next;
    public Node(int d)
    {
        data = d;
        next = null;
    }
}
  
// Linked list class
public class LinkedList
{
    Node head; // Head of list
  
    // Inserts a new node at the front of the list
    public void push(int new_data)
    {
        // Allocate new node and putting data
        Node new_node = new Node(new_data);
  
        // Make next of new node as head
        new_node.next = head;
  
        // Move the head to point to new Node
        head = new_node;
    }
  
    // Checks whether the value x is present in linked list
    public bool search(Node head, int x)
    {
        Node current = head; // Initialize current
        while (current != null)
        {
            if (current.data == x)
                return true; // data found
            current = current.next;
        }
        return false; // data not found
    }
  
    // Driver code
    public static void Main(String []args)
    {
  
        // Start with the empty list
        LinkedList llist = new LinkedList();
  
        /*Use push() to construct below list
        14->21->11->30->10 */
        llist.push(10);
        llist.push(30);
        llist.push(11);
        llist.push(21);
        llist.push(14);
  
        if (llist.search(llist.head, 21))
            Console.WriteLine("Yes");
        else
            Console.WriteLine("No");
    }
}
  
// This code contributed by Rajput-Ji

Javascript

  
// Iterative javascript program 
// to search an element
// in linked list
  
//Node class
class Node {
    constructor(d) {
        this.data = d;
        this.next = null;
    }
}
  
// Linked list class
  
    var head; // Head of list
  
    // Inserts a new node at the front of the list
    function push(new_data)
    {
        // Allocate new node and putting data
        var new_node = new Node(new_data);
  
        // Make next of new node as head
        new_node.next = head;
  
        // Move the head to point to new Node
        head = new_node;
    }
  
    // Checks whether the value 
    // x is present in linked list
    function search( head , x) 
    {
        var current = head; // Initialize current
        while (current != null) {
            if (current.data == x)
                return true; // data found
            current = current.next;
        }
        return false; // data not found
    }
  
    // Driver function to test
    // the above functions
      
  
        // Start with the empty list
        /*
          Use push() to construct below 
          list 14->21->11->30->10
         */
        push(10);
        push(30);
        push(11);
        push(21);
        push(14);
  
        if (search(head, 21))
            document.write("Yes");
        else
            document.write("No");
  
// This code contributed by aashish1995
  

输出：

Yes

递归解决方案

bool search(head, x)
1) If head is NULL, return false.
2) If head's key is same as x, return true;
3) Else return search(head->next, x) 

以下是上述算法的递归实现，用于搜索给定的键。

C++

// Recursive C++ program to search
// an element in linked list 
#include  
using namespace std;
  
/* Link list node */
struct Node 
{ 
    int key; 
    struct Node* next; 
}; 
  
/* Given a reference (pointer to pointer) to the head 
of a list and an int, push a new node on the front 
of the list. */
void push(struct Node** head_ref, int new_key) 
{ 
    /* allocate node */
    struct Node* new_node = 
            (struct Node*) malloc(sizeof(struct Node)); 
  
    /* put in the key */
    new_node->key = new_key; 
  
    /* link the old list off the new node */
    new_node->next = (*head_ref); 
  
    /* move the head to point to the new node */
    (*head_ref) = new_node; 
} 
  
/* Checks whether the value x is present in linked list */
bool search(struct Node* head, int x) 
{ 
    // Base case 
    if (head == NULL) 
        return false; 
      
    // If key is present in current node, return true 
    if (head->key == x) 
        return true; 
  
    // Recur for remaining list 
    return search(head->next, x); 
} 
  
/* Driver code*/
int main() 
{ 
    /* Start with the empty list */
    struct Node* head = NULL; 
    int x = 21; 
  
    /* Use push() to construct below list 
    14->21->11->30->10 */
    push(&head, 10); 
    push(&head, 30); 
    push(&head, 11); 
    push(&head, 21); 
    push(&head, 14); 
  
    search(head, 21)? cout << "Yes" : cout << "No"; 
    return 0; 
} 
  
// This code is contributed by SHUBHAMSINGH10

C

// Recursive C program to search an element in linked list
#include
#include
#include
/* Link list node */
struct Node
{
    int key;
    struct Node* next;
};
  
/* Given a reference (pointer to pointer) to the head
  of a list and an int, push a new node on the front
  of the list. */
void push(struct Node** head_ref, int new_key)
{
    /* allocate node */
    struct Node* new_node =
            (struct Node*) malloc(sizeof(struct Node));
  
    /* put in the key  */
    new_node->key  = new_key;
  
    /* link the old list off the new node */
    new_node->next = (*head_ref);
  
    /* move the head to point to the new node */
    (*head_ref)    = new_node;
}
  
/* Checks whether the value x is present in linked list */
bool search(struct Node* head, int x)
{
    // Base case
    if (head == NULL)
        return false;
      
    // If key is present in current node, return true
    if (head->key == x)
        return true;
  
    // Recur for remaining list
    return search(head->next, x);
}
  
/* Driver program to test count function*/
int main()
{
    /* Start with the empty list */
    struct Node* head = NULL;
    int x = 21;
  
    /* Use push() to construct below list
     14->21->11->30->10  */
    push(&head, 10);
    push(&head, 30);
    push(&head, 11);
    push(&head, 21);
    push(&head, 14);
  
    search(head, 21)? printf("Yes") : printf("No");
    return 0;
}

Java

// Recursive Java program to search an element
// in linked list
  
  
// Node class
class Node
{
    int data;
    Node next;
    Node(int d)
    {
        data = d;
        next = null;
    }
}
  
// Linked list class
class LinkedList
{
    Node head;    //Head of list
  
    //Inserts a new node at the front of the list
    public void push(int new_data)
    {
        //Allocate new node and putting data
        Node new_node = new Node(new_data);
  
        //Make next of new node as head
        new_node.next = head;
  
        //Move the head to point to new Node
        head = new_node;
    }
  
    // Checks whether the value x is present
    // in linked list
    public boolean search(Node head, int x)
    {
        // Base case
        if (head == null)
            return false;
  
        // If key is present in current node,
        // return true
        if (head.data == x)
            return true;
  
        // Recur for remaining list
        return search(head.next, x);
    }
  
    // Driver function to test the above functions
    public static void main(String args[])
    {
        // Start with the empty list
        LinkedList llist = new LinkedList();
  
        /* Use push() to construct below list
           14->21->11->30->10  */
        llist.push(10);
        llist.push(30);
        llist.push(11);
        llist.push(21);
        llist.push(14);
  
        if (llist.search(llist.head, 21))
            System.out.println("Yes");
        else
            System.out.println("No");
    }
}
// This code is contributed by Pratik Agarwal

Python

# Recursive Python program to 
# search an element in linked list
  
# Node class
class Node:
      
    # Function to initialise 
    # the node object
    def __init__(self, data):
        self.data = data # Assign data
        self.next = None # Initialize next as null
  
class LinkedList:
      
    def __init__(self):
        self.head = None # Initialize head as None
  
    # This function insert a new node at 
    # the beginning of the linked list
    def push(self, new_data):
      
        # Create a new Node
        new_node = Node(new_data)
  
        # Make next of new Node as head
        new_node.next = self.head
  
        # Move the head to 
        # point to new Node
        self.head = new_node
      
      
    # Checks whether the value key 
    # is present in linked list 
    def search(self, li, key):
          
        # Base case
        if(not li):
            return False
          
        # If key is present in 
        # current node, return true
        if(li.data == key):
            return True
          
        # Recur for remaining list
        return self.search(li.next, key)
      
# Driver Code            
if __name__=='__main__':
  
    li = LinkedList()
      
    li.push(1)
    li.push(2)
    li.push(3)
    li.push(4)
      
    key = 4
      
    if li.search(li.head,key):
        print("Yes")
    else:
        print("No")
      
# This code is contributed
# by Manoj Sharma

C＃

// Recursive C# program to search 
// an element in linked list
using System;
  
// Node class
public class Node
{
    public int data;
    public Node next;
    public Node(int d)
    {
        data = d;
        next = null;
    }
}
  
// Linked list class
public class LinkedList
{
    Node head; //Head of list
  
    //Inserts a new node at the front of the list
    public void push(int new_data)
    {
        //Allocate new node and putting data
        Node new_node = new Node(new_data);
  
        //Make next of new node as head
        new_node.next = head;
  
        //Move the head to point to new Node
        head = new_node;
    }
  
    // Checks whether the value x is present
    // in linked list
    public bool search(Node head, int x)
    {
        // Base case
        if (head == null)
            return false;
  
        // If key is present in current node,
        // return true
        if (head.data == x)
            return true;
  
        // Recur for remaining list
        return search(head.next, x);
    }
  
    // Driver code
    public static void Main()
    {
        // Start with the empty list
        LinkedList llist = new LinkedList();
  
        /* Use push() to construct below list
        14->21->11->30->10 */
        llist.push(10);
        llist.push(30);
        llist.push(11);
        llist.push(21);
        llist.push(14);
  
        if (llist.search(llist.head, 21))
            Console.WriteLine("Yes");
        else
            Console.WriteLine("No");
    }
}
  
// This code is contributed by PrinciRaj1992

Javascript

// Recursive javascript program to search an element
// in linked list
  
// Node class
 class Node {
        constructor(val) {
            this.data = val;
            this.next = null;
        }
    }
   
// Linked list class
var head; // Head of list
  
    // Inserts a new node at the front of the list
     function push(new_data) {
        // Allocate new node and putting data
var new_node = new Node(new_data);
  
        // Make next of new node as head
        new_node.next = head;
  
        // Move the head to povar to new Node
        head = new_node;
    }
  
    // Checks whether the value x is present
    // in linked list
     function search(head , x) {
        // Base case
        if (head == null)
            return false;
  
        // If key is present in current node,
        // return true
        if (head.data == x)
            return true;
  
        // Recur for remaining list
        return search(head.next, x);
    }
  
    // Driver function to test the above functions
      
        // Start with the empty list
          
  
        /*
         * Use push() to construct below list 14->21->11->30->10
         */
        push(10);
        push(30);
        push(11);
        push(21);
        push(14);
  
        if (search(head, 21))
            document.write("Yes");
        else
            document.write("No");
  
// This code contributed by gauravrajput1 

输出：

Yes

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