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.使用分配器a以及默认哈希函数、键相等谓词构造空表，并将il中的元素插入表中。
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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.使用分配器a以及默认哈希函数、键相等谓词构造空表，并将il中的元素插入表中。