Bharti Airtel Interview Preparation

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 length_of_longest_substring(s):
    char_index = {}
    max_len = 0
    start = 0
    for i, char in enumerate(s):
        if char in char_index:
            start = max(start, char_index[char] + 1)
        char_index[char] = i
        max_len = max(max_len, i - start + 1)
    return max_len

def reverse_list(head):
    prev = None
    curr = head
    while curr:
        next_temp = curr.next
        curr.next = prev
        prev = curr
        curr = next_temp
    return prev

def max_subarray(arr):
    max_sum = curr_sum = arr[0]
    for num in arr[1:]:
        curr_sum = max(num, curr_sum + num)
        max_sum = max(max_sum, curr_sum)
    return max_sum

def factorial(n):
    if n < 2:
        return 1
    return n * factorial(n-1)

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

def count_chars(s):
    return {c: s.count(c) for c in set(s)}