Constructs an empty table using `a` and default hash function and key equality predicate, and inserts the elements from `il` into it.
Constructs an empty table using `a` and default hash function and key equality predicate, and inserts the elements from `il` into it.构造一个使用分配器 `a`、默认哈希函数和默认键相等谓词的空哈希表，并将 `il` 中的元素插入其中。
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Constructs an empty table using `a` and default hash function and key equality predicate, and inserts the elements from `il` into it.构造一个使用分配器 `a`、默认哈希函数和默认键相等谓词的空哈希表，并将 `il` 中的元素插入其中。