Adding polynomials (with.Java)

This is an article about the “polynomial addition (with.Java)” problem.

As I solve coding test problems, I look back on the problems I solved and look into different solution methods to learn more.

Let’s look at the problem first.

problem

An expression consisting of the sum of one or more terms is called a polynomial.

When calculating a polynomial, calculate and organize like terms.

When a polynomial consisting of addition is given as a parameter, complete the solution function to return the result of adding like terms as a string.

If the expressions are the same, the shortest expression is returned.

Restrictions

• 0 < number in polynomial < 100
• Only ‘x’ variable exists in polynomial.
• A polynomial consists of a positive integer, a space, ‘x’, and ‘+’.
• There is always a space between the term and the operation symbol.
• The spaces are not consecutive and there are no spaces at the beginning or end.
• There is no case where a variable comes before a number in one term.
• Invalid input such as “ + 3xx + + x7 + “ will not be given.
• Numbers cannot start with 0.
• Multiplication between letters and numbers is omitted.
• A polynomial has only linear terms and constant terms.
• Coefficient 1 is omitted.
• The constant term in the result is placed last.
• 0 < length of polynomial < 50

Input/Output Example

My solution to the problem

class Solution {
 public String solution(String polynomial) {
 String answer = "";
 int xNum = 0;
 int num = 0;
 String[] strArr = polynomial.split(" ");
 for(String str : strArr){
 if(str.contains("x")){
 if(str.equals("x")){
 xNum += 1;
 }else{
 xNum += Integer.valueOf(str.replace("x", ""));
 }
 }else if(!str.equals("+")){
 num += Integer.valueOf(str);
 }
 }

 answer = (xNum != 0 ? xNum == 1 ? "x" : xNum + "x" : "") + (num != 0 ? (xNum != 0 ? " + " : "") + num : xNum == 0 ? "0" : "");
 return answer;
 }
}

Solution explanation

• String separation: Separates the given polynomials based on spaces and creates a string array.
• Terms processing: A loop is executed for each term, and terms containing x and constant terms are processed separately.
• Terms containing x: Accumulate the coefficients of x, distinguishing between cases where there is only “x” and cases where a number and “x” are combined.
• Constant term: If it is not “+” and does not contain “x”, the constant term is accumulated.
• Generate result string: Generate the final result string by combining the strings for the coefficients and constant terms of x.

Code pros and cons

• Advantages: We implemented logic that succinctly organizes polynomials, such as calculating each term appropriately and combining the results into a string. The code is written to be concise and easy to understand.
• Disadvantage: This code assumes that the input fits the given format. Exception handling is required when malformed input is given.