Java语言怎么实现扑克牌4张用加减乘除,使得得到的算式的结果是24,程序自动产生算式计算的实现的过程是什么
使用递归方式生成所有可能的表达式,并计算其结果
代码如下
import java.util.ArrayList;
import java.util.List;
public class Poker24Game {
private static final double TARGET = 24.0;
private static final double EPSILON = 1e-6;
public static void main(String[] args) {
int[] nums = {1, 2, 3, 4}; // 扑克牌的数字值
List<String> expressions = findExpressions(nums);
for (String expression : expressions) {
System.out.println(expression + " = " + TARGET);
}
}
public static List<String> findExpressions(int[] nums) {
List<String> expressions = new ArrayList<>();
helper(nums, new double[nums.length], 0, expressions);
return expressions;
}
private static void helper(int[] nums, double[] results, int count, List<String> expressions) {
if (count == nums.length) {
if (Math.abs(results[0] - TARGET) < EPSILON) {
String expression = buildExpression(results, nums);
expressions.add(expression);
}
return;
}
for (int i = 0; i < nums.length; i++) {
if (nums[i] == Integer.MAX_VALUE) {
continue;
}
int num = nums[i];
nums[i] = Integer.MAX_VALUE;
results[count] = num;
helper(nums, results, count + 1, expressions);
results[count] = -num;
helper(nums, results, count + 1, expressions);
results[count] = num;
for (int j = i + 1; j < nums.length; j++) {
if (nums[j] == Integer.MAX_VALUE) {
continue;
}
int nextNum = nums[j];
nums[j] = Integer.MAX_VALUE;
results[count] = num + nextNum;
helper(nums, results, count + 1, expressions);
results[count] = num - nextNum;
helper(nums, results, count + 1, expressions);
results[count] = num * nextNum;
helper(nums, results, count + 1, expressions);
if (nextNum != 0) {
results[count] = num / nextNum;
helper(nums, results, count + 1, expressions);
}
if (num != 0) {
results[count] = nextNum / num;
helper(nums, results, count + 1, expressions);
}
nums[j] = nextNum;
}
nums[i] = num;
}
}
private static String buildExpression(double[] results, int[] nums) {
StringBuilder sb = new StringBuilder();
for (int i = 0; i < results.length; i++) {
if (i > 0) {
if (results[i] >= 0) {
sb.append(" + ");
} else {
sb.append(" - ");
}
}
sb.append(Math.abs(results[i]));
}
for (int num : nums) {
sb.append(" = ").append(num);
}
return sb.toString();
}
}
不知道你这个问题是否已经解决, 如果还没有解决的话:要实现这个问题,我们可以通过回溯算法来生成所有可能的算式,并判断结果是否等于24。这里给出一个Java语言的实现过程。
import java.util.ArrayList;
import java.util.List;
public class GenerateExpression {
public static void main(String[] args) {
List<Integer> cards = new ArrayList<>();
cards.add(4);
cards.add(7);
cards.add(8);
cards.add(2);
List<String> expressions = generateExpressions(cards);
for (String expression : expressions) {
if (eval(expression) == 24) {
System.out.println(expression);
}
}
}
private static List<String> generateExpressions(List<Integer> cards) {
List<String> expressions = new ArrayList<>();
backtrack(cards, "", expressions);
return expressions;
}
private static void backtrack(List<Integer> cards, String expression, List<String> expressions) {
if (cards.size() == 1) {
expressions.add(expression + cards.get(0));
} else {
for (int i = 0; i < cards.size(); i++) {
int card = cards.get(i);
List<Integer> remainingCards = new ArrayList<>(cards);
remainingCards.remove(i);
// 递归生成所有可能的算式
backtrack(remainingCards, expression + card + "+", expressions);
backtrack(remainingCards, expression + card + "-", expressions);
backtrack(remainingCards, expression + card + "*", expressions);
backtrack(remainingCards, expression + card + "/", expressions);
}
}
}
private static double eval(String expression) {
try {
return (double) new javax.script.ScriptEngineManager()
.getEngineByName("JavaScript")
.eval(expression);
} catch (Exception e) {
return -1;
}
}
}
以上代码首先定义了generateExpressions
方法,该方法通过回溯算法生成所有可能的算式,然后定义了backtrack
方法来递归生成算式。
在main
方法中,我们定义了4张扑克牌的数字,并将其添加到一个列表中。然后调用generateExpressions
方法来生成所有可能的算式,再用eval
方法来计算每个算式的结果。最后,遍历算式结果,打印出结果等于24的算式。
以上是用Java语言实现一个程序,生成由扑克牌中的4张牌通过加减乘除操作得到结果为24的算式的解决方案。