Reverse a linked list
Problem Statement :
Given the pointer to the head node of a linked list, change the next pointers of the nodes so that their order is reversed. The head pointer given may be null meaning that the initial list is empty.
Example:
head references the list 1->2->3->Null.
Manipulate the next pointers of each node in place and return head, now referencing the head of the list 3->2->1->Null.
Function Description:
Complete the reverse function in the editor below.
reverse has the following parameter:
SinglyLinkedListNode pointer head: a reference to the head of a list
Returns
SinglyLinkedListNode pointer: a reference to the head of the reversed list
Input Format:
The first line contains an integer t, the number of test cases.
Each test case has the following format:
1. The first line contains an integer n, the number of elements in the linked list.
2. Each of the next n lines contains an integer, the data values of the elements in the linked list.
Constraints:
1. 1<=t<=10
2. 1<=n<=1000
3. 1<=list[i]<=1000
Solution :
Solution in C :
In C:
//the following function is all that is needed to complete the
//challenge in hackerrank platform.
SinglyLinkedListNode* reverse(SinglyLinkedListNode* head) {
struct SinglyLinkedListNode* new_head = NULL;
struct SinglyLinkedListNode* temp;
while(head != NULL){
temp = head->next;
head->next = new_head;
new_head = head;
head = temp;
}
return new_head;
}
In C++:
//the following function is all that is needed to complete the
//challenge in hackerrank platform.
Node* Reverse(Node *head)
{
// Complete this method
Node* prev = NULL;
Node* current = head;
Node* next;
while (current != NULL)
{
next = current->next;
current->next = prev;
prev = current;
current = next;
}
return prev;
}
In Java:
//the following method is all that is needed to complete the
//challenge in hackerrank platform.
static SinglyLinkedListNode reverse(SinglyLinkedListNode head) {
SinglyLinkedListNode next = null;
SinglyLinkedListNode current = head;
SinglyLinkedListNode previous = null;
while(current!=null)
{
next = current.next;
current.next = previous;
previous = current;
current = next;
}
SinglyLinkedListNode singlyLinkedListNode = previous;
return singlyLinkedListNode;
}
In Python 3:
//the following method is all that is needed to complete the
//challenge in hackerrank platform.
def Reverse(head):
current = head
prev = None
next = None
while current is not None:
next = current.next
current.next = prev;
prev = current;
current = next;
return prev
View More Similar Problems
Find the Running Median
The median of a set of integers is the midpoint value of the data set for which an equal number of integers are less than and greater than the value. To find the median, you must first sort your set of integers in non-decreasing order, then: If your set contains an odd number of elements, the median is the middle element of the sorted sample. In the sorted set { 1, 2, 3 } , 2 is the median.
View Solution →Minimum Average Waiting Time
Tieu owns a pizza restaurant and he manages it in his own way. While in a normal restaurant, a customer is served by following the first-come, first-served rule, Tieu simply minimizes the average waiting time of his customers. So he gets to decide who is served first, regardless of how sooner or later a person comes. Different kinds of pizzas take different amounts of time to cook. Also, once h
View Solution →Merging Communities
People connect with each other in a social network. A connection between Person I and Person J is represented as . When two persons belonging to different communities connect, the net effect is the merger of both communities which I and J belongs to. At the beginning, there are N people representing N communities. Suppose person 1 and 2 connected and later 2 and 3 connected, then ,1 , 2 and 3 w
View Solution →Components in a graph
There are 2 * N nodes in an undirected graph, and a number of edges connecting some nodes. In each edge, the first value will be between 1 and N, inclusive. The second node will be between N + 1 and , 2 * N inclusive. Given a list of edges, determine the size of the smallest and largest connected components that have or more nodes. A node can have any number of connections. The highest node valu
View Solution →Kundu and Tree
Kundu is true tree lover. Tree is a connected graph having N vertices and N-1 edges. Today when he got a tree, he colored each edge with one of either red(r) or black(b) color. He is interested in knowing how many triplets(a,b,c) of vertices are there , such that, there is atleast one edge having red color on all the three paths i.e. from vertex a to b, vertex b to c and vertex c to a . Note that
View Solution →Super Maximum Cost Queries
Victoria has a tree, T , consisting of N nodes numbered from 1 to N. Each edge from node Ui to Vi in tree T has an integer weight, Wi. Let's define the cost, C, of a path from some node X to some other node Y as the maximum weight ( W ) for any edge in the unique path from node X to Y node . Victoria wants your help processing Q queries on tree T, where each query contains 2 integers, L and
View Solution →