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17 lines
715 B
17 lines
715 B
3 years ago
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# Hints
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## General
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- Upon fetching an entry using the `entry` method, the entry can be modified in-place after dereferencing it.
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- The `or_insert` [method](https://doc.rust-lang.org/std/collections/hash_map/enum.Entry.html#method.or_insert) inserts the given value in the case when the entry is vacant, and returns a mutable reference to the value in the entry.
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```rust
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*counter.entry(key).or_insert(0) += 1;
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```
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- The `or_default` [method](https://doc.rust-lang.org/std/collections/hash_map/enum.Entry.html#method.or_default) ensures a value is in the entry by inserting the default value if empty, and returns a mutable reference to the value in the entry.
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```rust
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*counter.entry(key).or_default() += 1;
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```
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