Update week1-05-read-path.md, fix typo (#104)

* Update week1-05-read-path.md, fix typo

* Update week1-04-sst.md

mini-lsm-book/src/week1-04-sst.md

@@ -38,7 +38,7 @@ The encoding of SST is like:
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 ```
 
-You also need to implement `estimated_size` function of `SsTableBuilder`, so that the caller can know when can it start a new SST to write data. The function don't need to be very accurate. Given the assumption that data blocks contain much more data than meta block, we can simply return the size of data blocks for `estimated_size`.
+You also need to implement `estimated_size` function of `SsTableBuilder`, so that the caller can know when can it start a new SST to write data. The function doesn't need to be very accurate. Given the assumption that data blocks contain much more data than meta block, we can simply return the size of data blocks for `estimated_size`.
 
 Besides SST builder, you will also need to complete the encoding/decoding of block metadata, so that `SsTableBuilder::build` can produce a valid SST file.
 

mini-lsm-book/src/week1-05-read-path.md

@@ -27,7 +27,7 @@ src/iterators/two_merge_iterator.rs
 
 You have already implemented a merge iterator that merges iterators of the same type (i.e., memtable iterators). Now that we have implemented the SST formats, we have both on-disk SST structures and in-memory memtables. When we scan from the storage engine, we will need to merge data from both memtable iterators and SST iterators into a single one. In this case, we need a `TwoMergeIterator<X, Y>` that merges two different types of iterators.
 
-You can implement `TwoMergeIterator` in `two_merge_iter.rs`. As we only have two iterators here, we do not need to maintain a binary heap. Instead, we can simply use a flag to indicate which iterator to read. Similar to `MergeIterator`, if the same key is found in both of the iterator, the first iterator takes the precedence.
+You can implement `TwoMergeIterator` in `two_merge_iterator.rs`. As we only have two iterators here, we do not need to maintain a binary heap. Instead, we can simply use a flag to indicate which iterator to read. Similar to `MergeIterator`, if the same key is found in both of the iterator, the first iterator takes the precedence.
 
 ## Task 2: Read Path - Scan