Constructs an empty container using `a` as the allocator and a maximum load factor of 1.0 and inserts the elements from `il` into it.
Constructs an empty container using `a` as the allocator and a maximum load factor of 1.0 and inserts the elements from `il` into it.使用 a 作为分配器，最大负载因子为 1.0，构造一个空容器，并将 il 中的元素插入其中。
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Constructs an empty container using `a` as the allocator and a maximum load factor of 1.0 and inserts the elements from `il` into it.使用 a 作为分配器，最大负载因子为 1.0，构造一个空容器，并将 il 中的元素插入其中。