Update README with LeetCode Daily Challenge

Author: jeremymanning

README.md

@@ -503,6 +503,7 @@ _**Note:** Our group is currently taking a break from grinding leetcode. The tab
 | November 2, 2025 | [2257](https://leetcode.com/problems/count-unguarded-cells-in-the-grid/description/?envType=daily-question) | [Click here](https://github.com/ContextLab/leetcode-solutions/tree/main/problems/2257) | 🟡 Medium |
 | November 3, 2025 | [1578](https://leetcode.com/problems/minimum-time-to-make-rope-colorful/description/?envType=daily-question) | [Click here](https://github.com/ContextLab/leetcode-solutions/tree/main/problems/1578) | 🟡 Medium |
 | November 4, 2025 | [3318](https://leetcode.com/problems/find-x-sum-of-all-k-long-subarrays-i/description/?envType=daily-question) | [Click here](https://github.com/ContextLab/leetcode-solutions/tree/main/problems/3318) | 🟢 Easy |
+| November 5, 2025 | [3321](https://leetcode.com/problems/find-x-sum-of-all-k-long-subarrays-ii/description/?envType=daily-question) | [Click here](https://github.com/ContextLab/leetcode-solutions/tree/main/problems/3321) | 🔴 Hard |
 
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