Games and physics simulations need to detect which objects are touching or overlapping. With nnn objects, checking every pair is O(n2)O(n^2)O(n2) comparisons, which gets expensive fast. A hundred objects means roughly 5,000 pair checks. A thousand means nearly 500,000.
Every route is registered to a dictionary like this:
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arr[idx++] = bucketArr[j];
习题链接：LeetCode 739. 每日温度