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Questions

Table of Contents

Introduction

This section contains questions that can be asked in an interview.

Random Questions

Swap an array of integers using recursion.

Ans:

    void swap(int *a, int *b) {
        int temp = *a;
        *a = *b;
        *b = temp;
    }

    void swapArray(int *arr, int start, int end) {
        if (start >= end) {
            return;
        }
        swap(&arr[start], &arr[end]);
        swapArray(arr, start + 1, end - 1);
    }

Leap Year

A leap year is a year that is divisible by 4, but not by 100, unless it is also divisible by 400. Write a function that takes a year as a parameter and returns true if the year is a leap year, and false otherwise.

def isLeapYear(year):
    return year % 4 == 0 and (year % 100 != 0 or year % 400 == 0)

Using the isLeapYear function, write a function that takes a year and print the following 4 leap years.

def printLeapYears(year):
    count = 0
    while count < 4:
        year += (4-(year%4))
        if isLeapYear(year):
            print(year)
            count += 1

What errors appear in compile time and what errors appear in runtime?

-Ans: Syntax errors appear in compile time. Runtime errors appear in runtime.

Two Sum

Write a function that takes an array of integers and a target integer and returns true if there are 2 integers in the array that add up to the target integer, and false otherwise.

  • O(n2) solution

    def twoSum(nums, target):
    for i in range(len(nums)):
        for j in range(i+1, len(nums)):
            if nums[i] + nums[j] == target:
                return True
    return False

  • O(n) solution

    def twoSum(nums, target):
    count = {}
    for num in nums:
        if num in count:
            return True
        else:
            count[target - num] = 1
    return False

Write a function takes two strings of numbers and returns which number is greater.

def compare(num1:str,num2:str):
    return num1 if int(num1) > int(num2) else num2

Most Frequent Integer

Write a function that takes an array of integers and returns the most frequent integer in the array.

def mostFrequent(nums):
    count = {}
    for num in nums:
        if num in count:
            count[num] += 1
        else:
            count[num] = 1
    return max(count, key=count.get)

Uncommon Characters

Write a function that takes two strings and returns a string that contains only the characters that are not common to both strings.

def uncommonChars(str1, str2):
    count = {}
    for char in str1:
        if char in count:
            count[char] += 1
        else:
            count[char] = 1
    for char in str2:
        if char in count:
            count[char] += 1
        else:
            count[char] = 1
    return ''.join([char for char in count if count[char] == 1])

IQ Questions

Swap two variables without using a temporary variable.

    void swap(int *a, int *b) {
        *a = *a + *b;
        *b = *a - *b;
        *a = *a - *b;
    }

The 8 balls problem

You have 8 balls. One of them is defective and weighs less than the others. You have a balance scale.

  • Find the defective ball in 3 weighings. Ans: Divide the balls into 2 groups of 4 balls each. Weigh the 2 groups. take the lighter group and divide it into 2 groups of 2 balls each. Weigh the 2 groups. Take the lighter group and divide it into 2 groups of 1 ball each. Weigh the 2 groups. The lighter ball is the defective ball.
  • Find the defective ball in 2 weighings. Ans: Divide the balls into 3 groups of (3,3,2), weigh the first 2 groups (3,3), if they are equal, then the defective ball is in the third group (2), otherwise the defective ball is in the lighter group (3). Divide the lighter group (3) into 2 groups of (1,1), weigh the 2 groups, if they are equal, then the defective ball is the one that was not weighed, otherwise the defective ball is the lighter ball.
  • Same strategy can be used for 12 balls, 27 balls, 81 balls, etc.

The 4 gallon jug problem

You have a 3 gallon jug and a 5 gallon jug. How can you measure out exactly 4 gallons?

  • Ans: Fill the 5 gallon jug and pour it into the 3 gallon jug until the 3 gallon jug is full. Empty the 3 gallon jug. Pour the remaining 2 gallons from the 5 gallon jug into the 3 gallon jug. Fill the 5 gallon jug and pour it into the 3 gallon jug until the 3 gallon jug is full. The 5 gallon jug now contains 4 gallons.

The flower field problem

You have a field in the first day of the year. You plant a flower in the field. The flower doubles in size every day. It takes 100 days for the flower to cover the entire field. How many days does it take for the flower to cover half the field?

  • Ans: 99 days. The flower doubles in size every day. On the 99th day, the flower covers half the field. On the 100th day, the flower covers the entire field.

The 3 cuts problem

You have a cake and you want to cut it into 8 equal pieces. You can only make 3 cuts. How can you cut the cake into 8 equal pieces?

  • Ans: Cut the cake into 4 equal pieces. Stack the 4 pieces on top of each other. Cut the cake into 4 equal pieces. Stack the 4 pieces on top of each other. Cut the cake into 4 equal pieces. The cake is now cut into 8 equal pieces.

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