feat: 题目浏览量统计 + 缓存中间件

Author: CodeJudge

backend/src/controllers/problemController.js

@@ -33,6 +33,9 @@ function getProblem(req, res) {
   const problem = queryOne('SELECT * FROM problems WHERE id = ?', [req.params.id]);
   if (!problem) return res.status(404).json({ error: '题目不存在' });
 
+  // Increment view count
+  try { run('UPDATE problems SET view_count = COALESCE(view_count, 0) + 1 WHERE id = ?', [req.params.id]); } catch {}
+
   let parsed = { ...problem };
   try { parsed.test_cases = JSON.parse(problem.test_cases); } catch { parsed.test_cases = []; }
   try { parsed.options = JSON.parse(problem.options); } catch { parsed.options = []; }

backend/src/middleware/cache.js

@@ -0,0 +1,26 @@
+// Simple in-memory cache
+const cache = new Map();
+
+function memoize(key, fn, ttlMs = 30000) {
+  const cached = cache.get(key);
+  if (cached && Date.now() - cached.ts < ttlMs) {
+    return cached.data;
+  }
+  const data = fn();
+  cache.set(key, { data, ts: Date.now() });
+  return data;
+}
+
+function invalidate(key) {
+  cache.delete(key);
+}
+
+// Every 5 min clean stale entries
+setInterval(() => {
+  const now = Date.now();
+  for (const [key, val] of cache) {
+    if (now - val.ts > 120000) cache.delete(key);
+  }
+}, 300000);
+
+module.exports = { memoize, invalidate };

frontend/src/pages/Problems.tsx

@@ -1,4 +1,4 @@
-import { useState, useEffect, useCallback } from 'react';
+import { useState, useEffect, useCallback, useRef } from 'react';
 import { useSearchParams } from 'react-router-dom';
 import {
   Search,