⚡ Bolt: [optimize random number generation]

.jules/bolt.md

@@ -0,0 +1,7 @@
+## 2025-05-15 - Hybrid Sampling for Unique Random Numbers
+**Learning:** Rejection sampling using a Set for unique random number generation suffers from the Coupon Collector's Problem, where performance degrades exponentially as the requested count approaches the range size due to increasing collisions.
+**Action:** Implement a hybrid strategy: use rejection sampling for sparse requests (<50% of range) to save memory, and switch to an exclusion-based strategy (like a partial Fisher-Yates shuffle) for dense requests to ensure (Count)$ performance.
+
+## 2025-05-15 - Avoid Cold Path Micro-optimizations
+**Learning:** Optimizing one-time setup functions (e.g., platform detection using regex on `navigator.userAgent`) is a micro-optimization that adds code complexity without improving the user experience or solving a real bottleneck.
+**Action:** Focus on "hot paths" (high-frequency loops, frequent event handlers, or heavy data processing) where performance gains are measurable and impactful.

random.html

@@ -49,22 +49,39 @@
 
     <script>
         function generateRandomNumbers() {
-            let minValue = parseInt(document.getElementById('minValue').value);
-            let maxValue = parseInt(document.getElementById('maxValue').value);
-            let count = parseInt(document.getElementById('count').value);
-            let randomNumbers = new Set();
+            const minValue = parseInt(document.getElementById('minValue').value);
+            const maxValue = parseInt(document.getElementById('maxValue').value);
+            const count = parseInt(document.getElementById('count').value);
 
-            if (isNaN(minValue) || isNaN(maxValue) || isNaN(count) || minValue >= maxValue || count <= 0 || count > (maxValue - minValue + 1)) {
+            const rangeSize = maxValue - minValue + 1;
+
+            if (isNaN(minValue) || isNaN(maxValue) || isNaN(count) || minValue >= maxValue || count <= 0 || count > rangeSize) {
                 document.getElementById('randomNumbers').innerText = '請確保輸入正確的數值範圍和數量';
                 return;
             }
 
-            while (randomNumbers.size < count) {
-                let randomNumber = Math.floor(Math.random() * (maxValue - minValue + 1)) + minValue;
-                randomNumbers.add(randomNumber);
+            let result = [];
+
+            // ⚡ Bolt: Use hybrid sampling to avoid the Coupon Collector's Problem.
+            // If requested count is high relative to range (> 50%), use exclusion sampling (array swap).
+            // Otherwise, use rejection sampling (Set) which is more memory efficient for sparse requests.
+            if (count > rangeSize / 2) {
+                const pool = Array.from({ length: rangeSize }, (_, i) => i + minValue);
+                for (let i = 0; i < count; i++) {
+                    const j = Math.floor(Math.random() * (rangeSize - i)) + i;
+                    [pool[i], pool[j]] = [pool[j], pool[i]];
+                }
+                result = pool.slice(0, count);
+            } else {
+                const randomNumbers = new Set();
+                while (randomNumbers.size < count) {
+                    const randomNumber = Math.floor(Math.random() * rangeSize) + minValue;
+                    randomNumbers.add(randomNumber);
+                }
+                result = Array.from(randomNumbers);
             }
 
-            document.getElementById('randomNumbers').innerText = Array.from(randomNumbers).join(', ');
+            document.getElementById('randomNumbers').innerText = result.join(', ');
         }
     </script>
 </body>