my-bitcoin-basic-script-executor

Ex1.java

package org.javatests;

import java.util.Stack;

public class Ex1 {
    public Boolean transactions(String input) {
        String[] arr = input.split(" ");

        final var stack = new Stack<Integer>();

        for (String s : arr) {
            String op = s.replace("OP_", "");
            if (op.chars().allMatch(Character::isDigit)) {
                Integer number = Integer.parseInt(op);
                stack.push(number);
            } else if (!stack.isEmpty()) {
                if (op.equals("EQUAL")) {
                    if (stack.pop().equals(stack.pop())) stack.push(1);
                    else stack.push(0);
                } else if (op.equals("ADD")) {
                    Integer res = stack.pop() + stack.pop();
                    stack.push(res);
                } else if (op.equals("SUB")) {
                    Integer top = stack.pop();
                    Integer second = stack.pop();
                    stack.push(second - top);
                } else if (op.equals("VERIFY")) {
                    if (stack.peek().equals(0)) return false;
                    else stack.pop();
                }
            }
        }

        return !stack.isEmpty() && stack.pop() != 0;
    }
}

Ex1Test.java

package org.javatests;

import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.CsvSource;

class Ex1Test {

    @ParameterizedTest
    @CsvSource({
            "OP_1 OP_2 OP_ADD,true",
            "OP_1 OP_1 OP_ADD OP_3 OP_EQUAL,false",
            "OP_3 OP_2 OP_SUB OP_1 OP_EQUAL,true",
            "OP_3 OP_2 OP_SUB OP_5 OP_ADD OP_5 OP_EQUAL,false",
            "OP_ADD,false",
            "OP_1 OP_2,true",
            "OP_0 OP_VERIFY OP_1,false",
            "OP_1 OP_VERIFY OP_2,true"

    })
    void test(String input, Boolean expected) {
        Ex1 ex = new Ex1();
        Assertions.assertEquals(expected, ex.transactions(input));
    }

}