在 Java 中使用随机和运算符创建方程

Question

我正在尝试创建一个方法来为我创建一个方程式，作为一个字符串。

例如，此方法将创建：

字符串公式 = "5 + 3";

那么换个方法就可以解决了。

我真的不知道如何创建字符串。我应该使用concat吗？

感谢大家的帮助。

public static String getEquation() {


    for(int i=0;i<7;i++){

    int rand = rng.nextInt(5);

    switch (rand) {

        case 0:
            operator = "+";
            break;
        case 1:
            operator = "-";
            break;
        case 2:
            operator = "*";
            break;
        case 3:
            operator = "/";
            break;
        case 4:
            operator = "(";
            break;
        case 5:
            operator = ")";
    }


}
     return formula;
}

Answer 1

写得真快，我想这应该能让你继续下去。不过，您必须处理括号的情况。我没有考虑到这一点。

import java.util.Random;

public class Test {

    static Random randomGenerator = new Random();
    static String operators = "+-*/P"; //p = parentheses pair

    public static char getRandomOperator() {
        return operators.charAt(randomGenerator.nextInt(operators.length()));
    }

    public static int getRandomNumber() {
        return randomGenerator.nextInt(100);
    }

    public static String createEquation() {
        //Just for proof of concept, let's do 3 operators
        String equation = "";
        int numOfOperators = 3;
        char operator = ' ';
        for (int i = 0; i < numOfOperators; i++) {
            equation += getRandomNumber();
            equation += getRandomOperator();
        }
        equation += getRandomNumber();
        return equation;
    }

    public static void main(String[] args) {
        String equation = createEquation();
        System.out.println(equation);
    }
}

我可能稍后有时间回来解决括号问题。现在我只打印 'P' 应该处理括号的地方。

编辑更新它以处理括号。我将把它粘贴在这里，以防你想保持它的旧方式。还在这里和那里做了一些调整。请注意，当涉及到括号时，我没有处理它来匹配确切数量的运算符。这意味着如果在循环完成抓取运算符时所有左括号都没有关闭，那么我会在末尾附加额外的括号。这可能导致超过 7 个运算符。您可能应该添加逻辑，将一对括号视为 1 个运算符或将 1 个括号视为单个运算符。享受吧。

import java.util.Random;

public class Test {

    static Random randomGenerator = new Random();
    static String operators = "+-*/()";
    static int opeatorStringLength = operators.length();

    public static char getRandomOperator() {
        return operators.charAt(randomGenerator.nextInt(opeatorStringLength));
    }

    public static int getRandomNumber() {
        return randomGenerator.nextInt(100);
    }

    public static String appendToEquation(String equation, String value1, String value2) {
        String temp = equation;
        temp += value1;
        temp += value2;
        return temp;
    }

    public static String createEquation(int numOfOperators) {
        String equation = "";
        char operator;
        int operand;
        int openParenCounter = 0;
        for (int i = 0; i < numOfOperators; i++) {
            operator = getRandomOperator();
            operand = getRandomNumber();
            if (operator == '(') {
                openParenCounter++;
                equation = appendToEquation(equation, Character.toString(operator), Integer.toString(operand));
            } else if (operator == ')') {
                if (openParenCounter == 0) { //Can't start off with a close parenthesis
                    openParenCounter++;
                    equation = appendToEquation(equation, "(", Integer.toString(operand));
                } else {
                    openParenCounter--;
                    equation = appendToEquation(equation, Integer.toString(operand), Character.toString(operator));
                }
            } else {
                equation = appendToEquation(equation, Integer.toString(operand), Character.toString(operator));
            }
        }
        equation += getRandomNumber();
        while (openParenCounter > 0) {
            equation += ")";
            openParenCounter--;
        }

        return equation;
    }

    public static void main(String[] args) {
        String equation;
        equation = createEquation(7); //The argument passed is the number of operators to use
        System.out.println(equation);
    }
}

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