Most important programming technical interview questions

python
def reverse_string(s):
    return s[::-1]

# Example
reverse_string("hello")  # Output: "olleh"

python
def is_prime(n):
    if n <= 1:
        return False
    for i in range(2, int(n**0.5) + 1):
        if n % i == 0:
            return False
    return True

# Example
is_prime(17)  # Output: True

python
def find_largest(arr):
    max_val = arr[0]
    for num in arr[1:]:
        if num > max_val:
            max_val = num
    return max_val

# Example
find_largest([1, 5, 3, 9, 2])  # Output: 9

python
def binary_search(arr, target):
    left, right = 0, len(arr) - 1
    while left <= right:
        mid = (left + right) // 2
        if arr[mid] == target:
            return mid
        elif arr[mid] < target:
            left = mid + 1
        else:
            right = mid - 1
    return -1

# Example
binary_search([1, 2, 3, 4, 5], 3)  # Output: 2

python
class Node:
    def __init__(self, val):
        self.val = val
        self.next = None

def has_cycle(head):
    slow = fast = head
    while fast and fast.next:
        slow = slow.next
        fast = fast.next.next
        if slow == fast:
            return True
    return False

python
def find_middle(head):
    slow = fast = head
    while fast and fast.next:
        slow = slow.next
        fast = fast.next.next
    return slow.val if slow else None

python
def are_anagrams(s1, s2):
    return sorted(s1) == sorted(s2)

# Example
are_anagrams("listen", "silent")  # Output: True

python
def merge_two_lists(l1, l2):
    dummy = current = Node(0)
    while l1 and l2:
        if l1.val < l2.val:
            current.next = l1
            l1 = l1.next
        else:
            current.next = l2
            l2 = l2.next
        current = current.next
    current.next = l1 or l2
    return dummy.next

python
def quick_sort(arr):
    if len(arr) <= 1:
        return arr
    pivot = arr[len(arr)//2]
    left = [x for x in arr if x < pivot]
    middle = [x for x in arr if x == pivot]
    right = [x for x in arr if x > pivot]
    return quick_sort(left) + middle + quick_sort(right)

# Example
quick_sort([3,6,8,10,1,2,1])  # Output: [1, 1, 2, 3, 6, 8, 10]