In this HackerRank Get Node Value problem if we have given pointers of the head of a linked list and a specific position, then we need to determine the data value at that position.
Problem solution in Python programming.
#!/bin/python3
import math
import os
import random
import re
import sys
class SinglyLinkedListNode:
def __init__(self, node_data):
self.data = node_data
self.next = None
class SinglyLinkedList:
def __init__(self):
self.head = None
self.tail = None
def insert_node(self, node_data):
node = SinglyLinkedListNode(node_data)
if not self.head:
self.head = node
else:
self.tail.next = node
self.tail = node
def print_singly_linked_list(node, sep, fptr):
while node:
fptr.write(str(node.data))
node = node.next
if node:
fptr.write(sep)
def getNode(head, position):
if not head:
return None
if not head.next:
return head.data
lst_len = 0
ptr = head
while ptr.next:
lst_len += 1
ptr = ptr.next
while lst_len > position:
head = head.next
lst_len -= 1
return head.data
if __name__ == '__main__':
fptr = open(os.environ['OUTPUT_PATH'], 'w')
tests = int(input())
for tests_itr in range(tests):
llist_count = int(input())
llist = SinglyLinkedList()
for _ in range(llist_count):
llist_item = int(input())
llist.insert_node(llist_item)
position = int(input())
result = getNode(llist.head, position)
fptr.write(str(result) + 'n')
fptr.close()
Problem solution in Java Programming.
import java.io.*;
import java.math.*;
import java.security.*;
import java.text.*;
import java.util.*;
import java.util.concurrent.*;
import java.util.regex.*;
public class Solution {
static class SinglyLinkedListNode {
public int data;
public SinglyLinkedListNode next;
public SinglyLinkedListNode(int nodeData) {
this.data = nodeData;
this.next = null;
}
}
static class SinglyLinkedList {
public SinglyLinkedListNode head;
public SinglyLinkedListNode tail;
public SinglyLinkedList() {
this.head = null;
this.tail = null;
}
public void insertNode(int nodeData) {
SinglyLinkedListNode node = new SinglyLinkedListNode(nodeData);
if (this.head == null) {
this.head = node;
} else {
this.tail.next = node;
}
this.tail = node;
}
}
public static void printSinglyLinkedList(SinglyLinkedListNode node, String sep, BufferedWriter bufferedWriter) throws IOException {
while (node != null) {
bufferedWriter.write(String.valueOf(node.data));
node = node.next;
if (node != null) {
bufferedWriter.write(sep);
}
}
}
static int getNode(SinglyLinkedListNode head, int positionFromTail) {
SinglyLinkedListNode fast = head;
SinglyLinkedListNode slow = head;
int pos = 0;
while (pos < positionFromTail) {
fast = fast.next;
pos++;
}
while (fast.next!=null) {
slow = slow.next;
fast = fast.next;
}
return slow.data;
}
private static final Scanner scanner = new Scanner(System.in);
public static void main(String[] args) throws IOException {
BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(System.getenv("OUTPUT_PATH")));
int tests = scanner.nextInt();
scanner.skip("(rn|[nru2028u2029u0085])?");
for (int testsItr = 0; testsItr < tests; testsItr++) {
SinglyLinkedList llist = new SinglyLinkedList();
int llistCount = scanner.nextInt();
scanner.skip("(rn|[nru2028u2029u0085])?");
for (int i = 0; i < llistCount; i++) {
int llistItem = scanner.nextInt();
scanner.skip("(rn|[nru2028u2029u0085])?");
llist.insertNode(llistItem);
}
int position = scanner.nextInt();
scanner.skip("(rn|[nru2028u2029u0085])?");
int result = getNode(llist.head, position);
bufferedWriter.write(String.valueOf(result));
bufferedWriter.newLine();
}
bufferedWriter.close();
scanner.close();
}
}
Problem solution in C++ programming.
#include <bits/stdc++.h>
using namespace std;
class SinglyLinkedListNode {
public:
int data;
SinglyLinkedListNode *next;
SinglyLinkedListNode(int node_data) {
this->data = node_data;
this->next = nullptr;
}
};
class SinglyLinkedList {
public:
SinglyLinkedListNode *head;
SinglyLinkedListNode *tail;
SinglyLinkedList() {
this->head = nullptr;
this->tail = nullptr;
}
void insert_node(int node_data) {
SinglyLinkedListNode* node = new SinglyLinkedListNode(node_data);
if (!this->head) {
this->head = node;
} else {
this->tail->next = node;
}
this->tail = node;
}
};
void print_singly_linked_list(SinglyLinkedListNode* node, string sep, ofstream& fout) {
while (node) {
fout << node->data;
node = node->next;
if (node) {
fout << sep;
}
}
}
void free_singly_linked_list(SinglyLinkedListNode* node) {
while (node) {
SinglyLinkedListNode* temp = node;
node = node->next;
free(temp);
}
}
int getNode(SinglyLinkedListNode* head, int positionFromTail) {
int n = 0;
SinglyLinkedListNode *tmp = head;
while(tmp) {n++; tmp = tmp->next;}
fprintf(stderr, "n: %dn", n);
int pos = n - positionFromTail-1;
fprintf(stderr, "Pos: %dn", pos);
while(pos--){head = head->next;}
return head->data;
}
int main()
{
ofstream fout(getenv("OUTPUT_PATH"));
int tests;
cin >> tests;
cin.ignore(numeric_limits<streamsize>::max(), 'n');
for (int tests_itr = 0; tests_itr < tests; tests_itr++) {
SinglyLinkedList* llist = new SinglyLinkedList();
int llist_count;
cin >> llist_count;
cin.ignore(numeric_limits<streamsize>::max(), 'n');
for (int i = 0; i < llist_count; i++) {
int llist_item;
cin >> llist_item;
cin.ignore(numeric_limits<streamsize>::max(), 'n');
llist->insert_node(llist_item);
}
int position;
cin >> position;
cin.ignore(numeric_limits<streamsize>::max(), 'n');
int result = getNode(llist->head, position);
fout << result << "n";
}
fout.close();
return 0;
}
Problem solution in C programming.
#include <assert.h>
#include <limits.h>
#include <math.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
char* readline();
typedef struct SinglyLinkedListNode SinglyLinkedListNode;
typedef struct SinglyLinkedList SinglyLinkedList;
struct SinglyLinkedListNode {
int data;
SinglyLinkedListNode* next;
};
struct SinglyLinkedList {
SinglyLinkedListNode* head;
SinglyLinkedListNode* tail;
};
SinglyLinkedListNode* create_singly_linked_list_node(int node_data) {
SinglyLinkedListNode* node = malloc(sizeof(SinglyLinkedListNode));
node->data = node_data;
node->next = NULL;
return node;
}
void insert_node_into_singly_linked_list(SinglyLinkedList** singly_linked_list, int node_data) {
SinglyLinkedListNode* node = create_singly_linked_list_node(node_data);
if (!(*singly_linked_list)->head) {
(*singly_linked_list)->head = node;
} else {
(*singly_linked_list)->tail->next = node;
}
(*singly_linked_list)->tail = node;
}
void print_singly_linked_list(SinglyLinkedListNode* node, char* sep, FILE* fptr) {
while (node) {
fprintf(fptr, "%d", node->data);
node = node->next;
if (node) {
fprintf(fptr, "%s", sep);
}
}
}
void free_singly_linked_list(SinglyLinkedListNode* node) {
while (node) {
SinglyLinkedListNode* temp = node;
node = node->next;
free(temp);
}
}
int getNode( SinglyLinkedListNode* head, int positionFromTail )
{
int total = 0;
SinglyLinkedListNode* nodePtr = head;
// get the number of the total number of node
while( nodePtr )
{
total++;
nodePtr = nodePtr->next;
}
nodePtr = head;
for( int indx = 0; indx < total-positionFromTail-1; indx++ )
{
nodePtr = nodePtr->next;
}
return nodePtr->data;
}
int main()
{
FILE* fptr = fopen(getenv("OUTPUT_PATH"), "w");
char* tests_endptr;
char* tests_str = readline();
int tests = strtol(tests_str, &tests_endptr, 10);
if (tests_endptr == tests_str || *tests_endptr != ' ') { exit(EXIT_FAILURE); }
for (int tests_itr = 0; tests_itr < tests; tests_itr++) {
SinglyLinkedList* llist = malloc(sizeof(SinglyLinkedList));
llist->head = NULL;
llist->tail = NULL;
char* llist_count_endptr;
char* llist_count_str = readline();
int llist_count = strtol(llist_count_str, &llist_count_endptr, 10);
if (llist_count_endptr == llist_count_str || *llist_count_endptr != ' ') { exit(EXIT_FAILURE); }
for (int i = 0; i < llist_count; i++) {
char* llist_item_endptr;
char* llist_item_str = readline();
int llist_item = strtol(llist_item_str, &llist_item_endptr, 10);
if (llist_item_endptr == llist_item_str || *llist_item_endptr != ' ') { exit(EXIT_FAILURE); }
insert_node_into_singly_linked_list(&llist, llist_item);
}
char* position_endptr;
char* position_str = readline();
int position = strtol(position_str, &position_endptr, 10);
if (position_endptr == position_str || *position_endptr != ' ') { exit(EXIT_FAILURE); }
int result = getNode(llist->head, position);
fprintf(fptr, "%dn", result);
}
fclose(fptr);
return 0;
}
char* readline() {
size_t alloc_length = 1024;
size_t data_length = 0;
char* data = malloc(alloc_length);
while (true) {
char* cursor = data + data_length;
char* line = fgets(cursor, alloc_length - data_length, stdin);
if (!line) { break; }
data_length += strlen(cursor);
if (data_length < alloc_length - 1 || data[data_length - 1] == 'n') { break; }
size_t new_length = alloc_length << 1;
data = realloc(data, new_length);
if (!data) { break; }
alloc_length = new_length;
}
if (data[data_length - 1] == 'n') {
data[data_length - 1] = ' ';
}
data = realloc(data, data_length);
return data;
}
Problem solution in JavaScript programming.
'use strict';
const fs = require('fs');
process.stdin.resume();
process.stdin.setEncoding('utf-8');
let inputString = '';
let currentLine = 0;
process.stdin.on('data', inputStdin => {
inputString += inputStdin;
});
process.stdin.on('end', _ => {
inputString = inputString.replace(/s*$/, '')
.split('n')
.map(str => str.replace(/s*$/, ''));
main();
});
function readLine() {
return inputString[currentLine++];
}
const SinglyLinkedListNode = class {
constructor(nodeData) {
this.data = nodeData;
this.next = null;
}
};
const SinglyLinkedList = class {
constructor() {
this.head = null;
this.tail = null;
}
insertNode(nodeData) {
const node = new SinglyLinkedListNode(nodeData);
if (this.head == null) {
this.head = node;
} else {
this.tail.next = node;
}
this.tail = node;
}
};
function printSinglyLinkedList(node, sep, ws) {
while (node != null) {
ws.write(String(node.data));
node = node.next;
if (node != null) {
ws.write(sep);
}
}
}
function getNode( head, position) {
var current = head;
var prev
var next
while(current) {
next = current.next;
current.next = prev;
prev = current;
current = next;
}
for(var i=0;i<position;i++){
prev = prev.next;
}
return prev.data;
}
function main() {
const ws = fs.createWriteStream(process.env.OUTPUT_PATH);
const tests = parseInt(readLine(), 10);
for (let testsItr = 0; testsItr < tests; testsItr++) {
const llistCount = parseInt(readLine(), 10);
let llist = new SinglyLinkedList();
for (let i = 0; i < llistCount; i++) {
const llistItem = parseInt(readLine(), 10);
llist.insertNode(llistItem);
}
const position = parseInt(readLine(), 10);
let result = getNode(llist.head, position);
ws.write(result + "n");
}
ws.end();
}