HDFC Bank Interview Preparation

SELECT column1, COUNT(*) 
FROM table_name 
GROUP BY column1 
HAVING COUNT(*) > 1;

SELECT DISTINCT salary FROM employees 
ORDER BY salary DESC 
LIMIT 1 OFFSET n-1;

SELECT e.* FROM employees e 
LEFT JOIN departments d ON e.dept_id = d.id 
WHERE d.id IS NULL;

def two_sum(nums, target):
    seen = {}
    for i, num in enumerate(nums):
        if target - num in seen:
            return [seen[target - num], i]
        seen[num] = i
    return []

# Method 1: Slicing
s = "hello"
print(s[::-1])  # "olleh"

# Method 2: Iteration
def reverse(s):
    return ''.join(reversed(s))

def is_palindrome(s):
    s = s.replace(" ", "").lower()
    return s == s[::-1]

def find_max(arr):
    return max(arr) if arr else None

SELECT * FROM employees 
WHERE salary > (SELECT AVG(salary) FROM employees);

s = "hello"
print(s.count('l'))  # 2

def remove_duplicates(arr):
    return list(set(arr))

def merge(arr1, arr2):
    result = []
    i = j = 0
    while i < len(arr1) and j < len(arr2):
        if arr1[i] <= arr2[j]:
            result.append(arr1[i])
            i += 1
        else:
            result.append(arr2[j])
            j += 1
    result.extend(arr1[i:])
    result.extend(arr2[j:])
    return result

def is_anagram(s1, s2):
    return sorted(s1) == sorted(s2)

def fibonacci(n):
    a, b = 0, 1
    fib = []
    for _ in range(n):
        fib.append(a)
        a, b = b, a + b
    return fib

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

def factorial(n):
    if n < 0:
        return -1
    if n == 0:
        return 1
    return n * factorial(n - 1)

def bubble_sort(arr):
    n = len(arr)
    for i in range(n):
        for j in range(n - i - 1):
            if arr[j] > arr[j + 1]:
                arr[j], arr[j + 1] = arr[j + 1], arr[j]
    return arr

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

def linear_search(arr, target):
    for i, val in enumerate(arr):
        if val == target:
            return i
    return -1

def gcd(a, b):
    while b:
        a, b = b, a % b
    return a

def lcm(a, b):
    return (a * b) // gcd(a, b)

def reverse_string(s):
    reversed_str = ""
    for char in s:
        reversed_str = char + reversed_str
    return reversed_str