Problems - Set 1

Easy

FizzBuzz

Given a positive integer A, return an array of strings with all the integers from 1 to N. But for multiples of 3 the array should have “Fizz” instead of the number. For the multiples of 5, the array should have “Buzz” instead of the number. For numbers which are multiple of 3 and 5 both, the array should have “FizzBuzz” instead of the number.

Example:

A = 5
Return: [1 2 Fizz 4 Buzz]

Method 1 - Using loop and if else

ArrayList<String> list = new ArrayList<>();

for (int i = 1; i <= A; i++) {
    if (i % 3 == 0 && i % 5 == 0) {
        list.add("FizzBuzz");
            } else if (i % 3 == 0) {
        list.add("Fizz");
            } else if (i % 5 == 0) {
        list.add("Buzz");
            } else {
        list.add(String.valueOf(i));
    }
}

Method 2 - Using StringBuilder for String Concatenation

Instead of performing multiple concatenations using + inside the if conditions, use a StringBuilder to construct the strings. This can improve performance when dealing with large datasets.

ArrayList<String> list = new ArrayList<>();

for (int i = 1; i <= A; i++) {
    StringBuilder sb = new StringBuilder();
    if (i % 3 == 0) sb.append("Fizz");
    if (i % 5 == 0) sb.append("Buzz");
    list.add(sb.length() > 0 ? sb.toString() : String.valueOf(i));
}

Method 3 - Using Streams (Java 8+)

If we want to use a more functional programming style, we can leverage Java Streams.

List<String> list = IntStream.rangeClosed(1, A)
    .mapToObj(i -> i % 3 == 0 && i % 5 == 0 ? "FizzBuzz" :
                 i % 3 == 0 ? "Fizz" :
                 i % 5 == 0 ? "Buzz" : String.valueOf(i))
    .collect(Collectors.toList());

Store and calculate mathematical expression

Write a function to add one simple mathematical expressions which are of the form Ax^a + Bx^b + . . . (where the coefficients and exponents can be any positive or negative real number). Store the input values into a proper data structure.

Method 1: Bad Implementation

// Store the expression as a single array of doubles, where the kth element
// corresponds to the coefficient of the x^k term in the expression.
// It does not support expressions with negative or non-integer exponents.
int[] sum(double[] expr1) {
    ...
}

// Store the expression as a set of two arrays, c oefficients and exponents
sum(double[] coeffsl, double[] expon1) {
    ...
}

Method 2: Better Implementation

// Design data structure for the expression
class ExprTerm {
    double coefficient;
    double exponent;
}

ExprTerm[] sum(ExprTerm[] exprl) {
    ...    
}