"Reversing a linked list is a very popular question. We have two approaches to reverse the linked list: Iterative approach and recursion approach.
Iterative approach (JavaScript)
function reverseLL(head){
if(head === null) return head;
let prv = null;
let next = null;
let cur = head;
while(cur){
next = cur.next; //backup
cur.next = prv;
prv = cur;
cur = next;
}
head = prv;
return head;
}
Recursion Approach (JS)
function reverseLLByRecursion("
Satyam S. - "Reversing a linked list is a very popular question. We have two approaches to reverse the linked list: Iterative approach and recursion approach.
Iterative approach (JavaScript)
function reverseLL(head){
if(head === null) return head;
let prv = null;
let next = null;
let cur = head;
while(cur){
next = cur.next; //backup
cur.next = prv;
prv = cur;
cur = next;
}
head = prv;
return head;
}
Recursion Approach (JS)
function reverseLLByRecursion("See full answer
"public static boolean isPalindrome(String str){
boolean flag = true;
int len = str.length()-1;
int j = len;
for(int i=0;i<=len/2;i++){
if(str.charAt(i)!=str.charAt(j--)){
flag = false;
break;
}
}
return flag;
}"
Sravanthi M. - "public static boolean isPalindrome(String str){
boolean flag = true;
int len = str.length()-1;
int j = len;
for(int i=0;i<=len/2;i++){
if(str.charAt(i)!=str.charAt(j--)){
flag = false;
break;
}
}
return flag;
}"See full answer
"
Compare alternate houses i.e for each house starting from the third, calculate the maximum money that can be stolen up to that house by choosing between:
Skipping the current house and taking the maximum money stolen up to the previous house.
Robbing the current house and adding its value to the maximum money stolen up to the house two steps back.
package main
import (
"fmt"
)
// rob function calculates the maximum money a robber can steal
func maxRob(nums []int) int {
ln"
VContaineers - "
Compare alternate houses i.e for each house starting from the third, calculate the maximum money that can be stolen up to that house by choosing between:
Skipping the current house and taking the maximum money stolen up to the previous house.
Robbing the current house and adding its value to the maximum money stolen up to the house two steps back.
package main
import (
"fmt"
)
// rob function calculates the maximum money a robber can steal
func maxRob(nums []int) int {
ln"See full answer
"We can use dictionary to store cache items so that our read / write operations will be O(1).
Each time we read or update an existing record, we have to ensure the item is moved to the back of the cache. This will allow us to evict the first item in the cache whenever the cache is full and we need to add new records also making our eviction O(1)
Instead of normal dictionary, we will use ordered dictionary to store cache items. This will allow us to efficiently move items to back of the cache a"
Alfred O. - "We can use dictionary to store cache items so that our read / write operations will be O(1).
Each time we read or update an existing record, we have to ensure the item is moved to the back of the cache. This will allow us to evict the first item in the cache whenever the cache is full and we need to add new records also making our eviction O(1)
Instead of normal dictionary, we will use ordered dictionary to store cache items. This will allow us to efficiently move items to back of the cache a"See full answer
"Use a representative of each, e.g. sort the string and add it to the value of a hashmap> where we put all the words that belong to the same anagram together."
Gaston B. - "Use a representative of each, e.g. sort the string and add it to the value of a hashmap> where we put all the words that belong to the same anagram together."See full answer
"Idea for solution:
Reverse the complete char array
Reverse the words separated by space. i.e. Find the space characters and the reverse the subarray between two space characters.
vector reverseSubarray(vector& arr, int s, int e)
{
while (s reverseWords(vector& arr )
{
int n = arr.size();
reverse(arr, 0, n - 1"
Rahul M. - "Idea for solution:
Reverse the complete char array
Reverse the words separated by space. i.e. Find the space characters and the reverse the subarray between two space characters.
vector reverseSubarray(vector& arr, int s, int e)
{
while (s reverseWords(vector& arr )
{
int n = arr.size();
reverse(arr, 0, n - 1"See full answer
"Initialize left pointer: Set a left pointer left to 0.
Iterate through the array: Iterate through the array from left to right.
If the current element is not 0, swap it with the element at the left pointer and increment left.
Time complexity: O(n). The loop iterates through the entire array once, making it linear time.
Space complexity: O(1). The algorithm operates in-place, modifying the input array directly without using additional data structures.
"
Avon T. - "Initialize left pointer: Set a left pointer left to 0.
Iterate through the array: Iterate through the array from left to right.
If the current element is not 0, swap it with the element at the left pointer and increment left.
Time complexity: O(n). The loop iterates through the entire array once, making it linear time.
Space complexity: O(1). The algorithm operates in-place, modifying the input array directly without using additional data structures.
"See full answer
"\# Definition for a binary tree node.
class TreeNode:
def init(self, val=0, left=None, right=None):
self.val = val
self.left = left
self.right = right
class Solution:
def maxPathSum(self, root: TreeNode) -> int:
self.max_sum = float('-inf')"
Jerry O. - "\# Definition for a binary tree node.
class TreeNode:
def init(self, val=0, left=None, right=None):
self.val = val
self.left = left
self.right = right
class Solution:
def maxPathSum(self, root: TreeNode) -> int:
self.max_sum = float('-inf')"See full answer
"function findPrimes(n) {
if (n < 2) return [];
const primes = [];
for (let i=2; i <= n; i++) {
const half = Math.floor(i/2);
let isPrime = true;
for (let prime of primes) {
if (i % prime === 0) {
isPrime = false;
break;
}
}
if (isPrime) {
primes.push(i);
}
}
return primes;
}
`"
Tiago R. - "function findPrimes(n) {
if (n < 2) return [];
const primes = [];
for (let i=2; i <= n; i++) {
const half = Math.floor(i/2);
let isPrime = true;
for (let prime of primes) {
if (i % prime === 0) {
isPrime = false;
break;
}
}
if (isPrime) {
primes.push(i);
}
}
return primes;
}
`"See full answer
"
from typing import List
def getnumberof_islands(binaryMatrix: List[List[int]]) -> int:
if not binaryMatrix: return 0
rows = len(binaryMatrix)
cols = len(binaryMatrix[0])
islands = 0
for r in range(rows):
for c in range(cols):
if binaryMatrixr == 1:
islands += 1
dfs(binaryMatrix, r, c)
return islands
def dfs(grid, r, c):
if (
r = len(grid)
"
Rick E. - "
from typing import List
def getnumberof_islands(binaryMatrix: List[List[int]]) -> int:
if not binaryMatrix: return 0
rows = len(binaryMatrix)
cols = len(binaryMatrix[0])
islands = 0
for r in range(rows):
for c in range(cols):
if binaryMatrixr == 1:
islands += 1
dfs(binaryMatrix, r, c)
return islands
def dfs(grid, r, c):
if (
r = len(grid)
"See full answer
"Problem Statement: The Fibonacci sequence is defined as F(n) = F(n-1) + F(n-2) with F(0) = 1 and F(1) = 1.
The solution is given in the problem statement itself.
If the value of n = 0, return 1.
If the value of n = 1, return 1.
Otherwise, return the sum of data at (n - 1) and (n - 2).
Explanation: The Fibonacci sequence is a series of numbers where each number is the sum of the two preceding ones, typically starting with 0 and 1.
Java Solution:
public static int fib(int n"
Rishi G. - "Problem Statement: The Fibonacci sequence is defined as F(n) = F(n-1) + F(n-2) with F(0) = 1 and F(1) = 1.
The solution is given in the problem statement itself.
If the value of n = 0, return 1.
If the value of n = 1, return 1.
Otherwise, return the sum of data at (n - 1) and (n - 2).
Explanation: The Fibonacci sequence is a series of numbers where each number is the sum of the two preceding ones, typically starting with 0 and 1.
Java Solution:
public static int fib(int n"See full answer
"A much better solution than the one in the article, below:
It looks like the ones writing articles here in Javascript do not understand the time/space complexity of javascript methods.
shift, splice, sort, etc... In the solution article you have a shift and a sort being done inside a while, that is, the multiplication of Ns.
My solution, below, iterates through the list once and then sorts it, separately. It´s O(N+Log(N))
class ListNode {
constructor(val = 0, next = null) {
th"
Guilherme F. - "A much better solution than the one in the article, below:
It looks like the ones writing articles here in Javascript do not understand the time/space complexity of javascript methods.
shift, splice, sort, etc... In the solution article you have a shift and a sort being done inside a while, that is, the multiplication of Ns.
My solution, below, iterates through the list once and then sorts it, separately. It´s O(N+Log(N))
class ListNode {
constructor(val = 0, next = null) {
th"See full answer
"bool isValidBST(TreeNode* root, long min = LONGMIN, long max = LONGMAX){
if (root == NULL)
return true;
if (root->val val >= max)
return false;
return isValidBST(root->left, min, root->val) &&
isValidBST(root->right, root->val, max);
}
`"
Alvaro R. - "bool isValidBST(TreeNode* root, long min = LONGMIN, long max = LONGMAX){
if (root == NULL)
return true;
if (root->val val >= max)
return false;
return isValidBST(root->left, min, root->val) &&
isValidBST(root->right, root->val, max);
}
`"See full answer