本文旨在提供一种使用Java和递归算法，计算基于JSON配置的问卷调查中所有可能的路径数量的解决方案。我们将深入探讨如何解析JSON结构，并使用递归函数遍历所有可能的答案分支，最终计算出完成问卷调查的不同方式的总数。此外，还将讨论在设计此类问卷调查逻辑时的一些注意事项。
理解JSON问卷结构
首先，我们需要理解JSON问卷的结构。在提供的例子中，JSON对象的键表示问题，而键对应的值又是一个JSON对象，该对象的键表示问题的答案，值则表示下一个问题。如果值为以"0 "开头的字符串，则表示问卷结束。
{
"What is your marital status?": {
"Single": "Are you planning on getting married next year?",
"Married": "How long have you been married?"
},
"Are you planning on getting married next year?": {
"Yes": "0 Thanks for your answers! We hope that you will build a cool family!",
"No": "0 Thanks for your answers! Who knows, maybe you'll find someone significant in your life!"
},
"How long have you been married?": {
"Less than a year": "0 Thanks for your answers! We hope that you will celebrate your one year anniversary soon!",
"More than a year": "Have you celebrated your one year anniversary?"
},
"Have you celebrated your one year anniversary?": {
"Yes": "0 Wow, cool! Keep it up! Thanks for your answers.",
"No": "0 We think you should fix it next time! Thanks for your answers!"
}
}递归计算路径数
为了计算所有可能的路径，我们可以使用递归函数。该函数接受JSON节点和当前问题作为参数。
- 基本情况: 如果当前问题没有对应的答案（即，到达问卷的末尾），则返回1，表示找到了一条有效路径。
- 递归步骤: 如果当前问题有对应的答案，则遍历所有可能的答案。对于每个答案，递归调用该函数，并将下一个问题作为参数传递。将所有递归调用的结果相加，得到总的路径数。
以下是Java代码示例，使用了Jackson库来解析JSON：
立即学习“Java免费学习笔记（深入）”；
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import java.io.IOException;
import java.util.concurrent.atomic.AtomicInteger;
public class QuizService {
public static int countWays(JsonNode node, String question) {
JsonNode answers = node.get(question);
if (answers == null) {
return 1;
}
AtomicInteger ways = new AtomicInteger();
answers.fields().forEachRemaining(answer ->
ways.addAndGet(countWays(node, answer.getValue().asText())));
return ways.get();
}
public static void main(String[] args) throws IOException {
String jsonString = "{" +
" \"What is your marital status?\": {" +
" \"Single\": \"Are you planning on getting married next year?\"," +
" \"Married\": \"How long have you been married?\"" +
" }," +
" \"Are you planning on getting married next year?\": {" +
" \"Yes\": \"0 Thanks for your answers! We hope that you will build a cool family!\"," +
" \"No\": \"0 Thanks for your answers! Who knows, maybe you'll find someone significant in your life!\"" +
" }," +
" \"How long have you been married?\": {" +
" \"Less than a year\": \"0 Thanks for your answers! We hope that you will celebrate your one year anniversary soon!\"," +
" \"More than a year\": \"Have you celebrated your one year anniversary?\"" +
" }," +
" \"Have you celebrated your one year anniversary?\": {" +
" \"Yes\": \"0 Wow, cool! Keep it up! Thanks for your answers.\"," +
" \"No\": \"0 We think you should fix it next time! Thanks for your answers!\"" +
" }" +
"}";
ObjectMapper mapper = new ObjectMapper();
JsonNode node = mapper.readTree(jsonString);
System.out.println(countWays(node, "What is your marital status?")); // Output: 4
}
}代码解释:
- countWays(JsonNode node, String question): 递归函数，用于计算从给定问题开始的路径数。
- JsonNode answers = node.get(question);: 获取当前问题的所有答案。
- if (answers == null): 如果当前问题没有答案，说明到达了问卷的终点，返回1。
- answers.fields().forEachRemaining(answer -> ...): 遍历所有可能的答案。
- ways.addAndGet(countWays(node, answer.getValue().asText())): 递归调用 countWays 函数，并将下一个问题作为参数传递。
- ObjectMapper mapper = new ObjectMapper();: 创建 Jackson ObjectMapper 对象，用于解析 JSON 字符串。
- JsonNode node = mapper.readTree(jsonString);: 将 JSON 字符串解析为 JsonNode 对象。
设计注意事项
- 循环依赖: 在设计问卷结构时，需要避免循环依赖，否则递归函数可能会无限循环。例如，问题A的答案指向问题B，问题B的答案又指向问题A。
- 性能: 对于非常复杂的问卷，递归可能会导致栈溢出。在这种情况下，可以考虑使用迭代的方式来解决。
- 错误处理: 在实际应用中，需要添加错误处理机制，例如处理JSON解析错误、处理找不到问题等情况。
- JSON结构验证: 应该在代码中加入JSON结构验证，确保JSON文件符合预期的格式。
总结
本文介绍了一种使用Java和递归算法，计算基于JSON配置的问卷调查中所有可能的路径数量的方法。通过理解JSON结构和递归算法，我们可以轻松地计算出完成问卷调查的不同方式的总数。同时，我们也讨论了在设计此类问卷调查逻辑时的一些注意事项，以确保问卷的正确性和性能。
