The Top 5 Most Common Coding Interview Questions and How to Answer Them

Are you preparing for a coding interview at a top tech company like FANG? Do you want to know the most common coding interview questions and how to answer them? Look no further! In this article, we will discuss the top 5 most common coding interview questions and provide you with tips on how to answer them.

Question 1: Reverse a String

The first question that often comes up in coding interviews is to reverse a string. This question tests your ability to manipulate strings and use loops effectively. Here's an example of how to reverse a string in Python:

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

This code uses slicing to reverse the string. The [::-1] syntax means to start at the end of the string and move backwards with a step of -1, effectively reversing the string.

Another way to reverse a string is to use a loop:

def reverse_string(s):
    result = ""
    for i in range(len(s)-1, -1, -1):
        result += s[i]
    return result

This code uses a for loop to iterate over the string in reverse order and build a new string with the characters in reverse order.

Question 2: Find the Maximum Value in an Array

The second question that often comes up in coding interviews is to find the maximum value in an array. This question tests your ability to use loops and conditionals effectively. Here's an example of how to find the maximum value in an array in Python:

def find_max(arr):
    max_val = arr[0]
    for i in range(1, len(arr)):
        if arr[i] > max_val:
            max_val = arr[i]
    return max_val

This code uses a for loop to iterate over the array and a conditional to check if each element is greater than the current maximum value. If it is, the current element becomes the new maximum value.

Question 3: Check if a String is a Palindrome

The third question that often comes up in coding interviews is to check if a string is a palindrome. This question tests your ability to manipulate strings and use loops effectively. Here's an example of how to check if a string is a palindrome in Python:

def is_palindrome(s):
    return s == s[::-1]

This code uses slicing to reverse the string and then checks if the reversed string is equal to the original string. If they are equal, the string is a palindrome.

Another way to check if a string is a palindrome is to use two pointers:

def is_palindrome(s):
    i = 0
    j = len(s) - 1
    while i < j:
        if s[i] != s[j]:
            return False
        i += 1
        j -= 1
    return True

This code uses two pointers to iterate over the string from both ends and check if the characters at each position are equal. If they are not equal, the string is not a palindrome.

Question 4: Reverse a Linked List

The fourth question that often comes up in coding interviews is to reverse a linked list. This question tests your ability to manipulate linked lists and use pointers effectively. Here's an example of how to reverse a linked list in Python:

class ListNode:
    def __init__(self, val=0, next=None):
        self.val = val
        self.next = next

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

This code uses three pointers to iterate over the linked list and reverse the direction of the pointers. The prev pointer starts as None, the curr pointer starts at the head of the linked list, and the next_node pointer is used to keep track of the next node in the original linked list. The curr.next = prev line reverses the direction of the pointer, and the prev = curr and curr = next_node lines move the pointers to the next nodes in the original linked list.

Question 5: Merge Two Sorted Arrays

The fifth question that often comes up in coding interviews is to merge two sorted arrays. This question tests your ability to manipulate arrays and use loops effectively. Here's an example of how to merge two sorted arrays in Python:

def merge_arrays(arr1, arr2):
    result = []
    i = 0
    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 += arr1[i:]
    result += arr2[j:]
    return result

This code uses two pointers to iterate over the two arrays and compare the values at each position. The result array is used to store the merged array, and the i and j pointers are used to keep track of the current positions in the two arrays. The while loop continues until one of the pointers reaches the end of its array. The result += arr1[i:] and result += arr2[j:] lines add any remaining elements from the two arrays to the result array.

Conclusion

In this article, we discussed the top 5 most common coding interview questions and provided you with tips on how to answer them. These questions test your ability to manipulate strings, arrays, and linked lists, and use loops, conditionals, and pointers effectively. By practicing these questions and understanding the solutions, you will be better prepared for your coding interview and increase your chances of success. Good luck!

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