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Merge remote-tracking branch 'upstream/master'
2 parents 9ba8b54 + 98c0d55 commit d01fb8d

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31 files changed

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‎B-Tree/BTree.playground/Contents.swift

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import Foundation
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// last checked with Xcode 9.0b4
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#if swift(>=4.0)
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print("Hello, Swift 4!")
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#endif
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// last checked with Xcode 10.0
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let bTree = BTree<Int, Int>(order: 1)!
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‎B-Tree/BTree.playground/playground.xcworkspace/xcshareddata/IDEWorkspaceChecks.plist

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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
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<plist version="1.0">
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<dict>
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<key>IDEDidComputeMac32BitWarning</key>
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<true/>
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</dict>
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</plist>

‎B-Tree/Tests/Tests.xcodeproj/project.pbxproj

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isa = PBXProject;
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attributes = {
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LastSwiftUpdateCheck = 0730;
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LastUpgradeCheck = 0800;
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LastUpgradeCheck = 1000;
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ORGANIZATIONNAME = "Viktor Szilárd Simkó";
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TargetAttributes = {
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C66702771D0EEE25008CD769 = {
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CreatedOnToolsVersion = 7.3.1;
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LastSwiftMigration = 0800;
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LastSwiftMigration = 1000;
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};
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};
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};
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CLANG_CXX_LIBRARY = "libc++";
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CLANG_ENABLE_MODULES = YES;
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CLANG_ENABLE_OBJC_ARC = YES;
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CLANG_WARN_BLOCK_CAPTURE_AUTORELEASING = YES;
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CLANG_WARN_BOOL_CONVERSION = YES;
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CLANG_WARN_COMMA = YES;
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CLANG_WARN_CONSTANT_CONVERSION = YES;
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CLANG_WARN_DEPRECATED_OBJC_IMPLEMENTATIONS = YES;
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CLANG_WARN_DIRECT_OBJC_ISA_USAGE = YES_ERROR;
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CLANG_WARN_EMPTY_BODY = YES;
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CLANG_WARN_ENUM_CONVERSION = YES;
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CLANG_WARN_INFINITE_RECURSION = YES;
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CLANG_WARN_INT_CONVERSION = YES;
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CLANG_WARN_NON_LITERAL_NULL_CONVERSION = YES;
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CLANG_WARN_OBJC_IMPLICIT_RETAIN_SELF = YES;
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CLANG_WARN_OBJC_LITERAL_CONVERSION = YES;
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CLANG_WARN_OBJC_ROOT_CLASS = YES_ERROR;
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CLANG_WARN_RANGE_LOOP_ANALYSIS = YES;
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CLANG_WARN_STRICT_PROTOTYPES = YES;
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CLANG_WARN_SUSPICIOUS_MOVE = YES;
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CLANG_WARN_UNREACHABLE_CODE = YES;
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CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
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CLANG_CXX_LIBRARY = "libc++";
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CLANG_ENABLE_MODULES = YES;
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CLANG_ENABLE_OBJC_ARC = YES;
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CLANG_WARN_BLOCK_CAPTURE_AUTORELEASING = YES;
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CLANG_WARN_BOOL_CONVERSION = YES;
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CLANG_WARN_COMMA = YES;
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CLANG_WARN_CONSTANT_CONVERSION = YES;
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CLANG_WARN_DEPRECATED_OBJC_IMPLEMENTATIONS = YES;
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CLANG_WARN_DIRECT_OBJC_ISA_USAGE = YES_ERROR;
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CLANG_WARN_EMPTY_BODY = YES;
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CLANG_WARN_ENUM_CONVERSION = YES;
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CLANG_WARN_INFINITE_RECURSION = YES;
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CLANG_WARN_INT_CONVERSION = YES;
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CLANG_WARN_NON_LITERAL_NULL_CONVERSION = YES;
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CLANG_WARN_OBJC_IMPLICIT_RETAIN_SELF = YES;
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CLANG_WARN_OBJC_LITERAL_CONVERSION = YES;
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CLANG_WARN_OBJC_ROOT_CLASS = YES_ERROR;
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CLANG_WARN_RANGE_LOOP_ANALYSIS = YES;
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CLANG_WARN_STRICT_PROTOTYPES = YES;
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CLANG_WARN_SUSPICIOUS_MOVE = YES;
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CLANG_WARN_UNREACHABLE_CODE = YES;
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CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
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PRODUCT_BUNDLE_IDENTIFIER = viktorsimko.Tests;
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PRODUCT_NAME = "$(TARGET_NAME)";
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SWIFT_OPTIMIZATION_LEVEL = "-Onone";
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SWIFT_VERSION = 4.0;
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SWIFT_VERSION = 4.2;
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};
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name = Debug;
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};
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LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/../Frameworks @loader_path/../Frameworks";
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PRODUCT_BUNDLE_IDENTIFIER = viktorsimko.Tests;
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PRODUCT_NAME = "$(TARGET_NAME)";
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SWIFT_VERSION = 4.0;
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SWIFT_VERSION = 4.2;
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};
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name = Release;
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};

‎B-Tree/Tests/Tests.xcodeproj/project.xcworkspace/xcshareddata/IDEWorkspaceChecks.plist

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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
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<plist version="1.0">
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<dict>
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<key>IDEDidComputeMac32BitWarning</key>
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<true/>
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</dict>
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</plist>

‎B-Tree/Tests/Tests.xcodeproj/xcshareddata/xcschemes/Tests.xcscheme

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<?xml version="1.0" encoding="UTF-8"?>
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<Scheme
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LastUpgradeVersion = "0800"
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LastUpgradeVersion = "1000"
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version = "1.3">
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<BuildAction
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parallelizeBuildables = "YES"

‎Bloom Filter/BloomFilter.playground/Contents.swift

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//: Playground - noun: a place where people can play
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// last checked with Xcode 9.0b4
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#if swift(>=4.0)
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print("Hello, Swift 4!")
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#endif
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public class BloomFilter<T> {
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fileprivate var array: [Bool]
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private var hashFunctions: [(T) -> Int]
@@ -54,15 +51,15 @@ public class BloomFilter<T> {
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func djb2(x: String) -> Int {
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var hash = 5381
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for char in x.characters {
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for char in x {
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hash = ((hash << 5) &+ hash) &+ char.hashValue
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}
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return Int(hash)
6158
}
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func sdbm(x: String) -> Int {
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var hash = 0
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for char in x.characters {
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for char in x {
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hash = char.hashValue &+ (hash << 6) &+ (hash << 16) &- hash
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}
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return Int(hash)

‎Bloom Filter/BloomFilter.playground/playground.xcworkspace/xcshareddata/IDEWorkspaceChecks.plist

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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
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<plist version="1.0">
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<dict>
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<key>IDEDidComputeMac32BitWarning</key>
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<true/>
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</dict>
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</plist>

‎Bloom Filter/BloomFilter.playground/timeline.xctimeline

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This file was deleted.

‎Bloom Filter/README.markdown

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If you're coming from another imperative language, you might notice the unusual syntax in the `exists` assignment. Swift makes use of functional paradigms when it makes code more consise and readable, and in this case `reduce` is a much more consise way to check if all the required bits are `true` than a `for` loop.
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103-
*Written for Swift Algorithm Club by Jamil Dhanani. Edited by Matthijs Hollemans.*
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## Another approach
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In the previous section, you learnt about how using multiple different hash functions can help reduce the chance of collisions in the bloom filter. However, good hash functions are difficult to design. A simple alternative to multiple hash functions is to use a set of random numbers.
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As an example, let's say a bloom filter wants to hash each element 15 times during insertion. Instead of using 15 different hash functions, you can rely on just one hash function. The hash value can then be combined with 15 different values to form the indices for flipping. This bloom filter would initialize a set of 15 random numbers ahead of time and use these values during each insertion.
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```
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hash("Hello world!") >> hash(987654321) // would flip bit 8
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hash("Hello world!") >> hash(123456789) // would flip bit 2
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```
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Since Swift 4.2, `Hasher` is now included in the Standard library, which is designed to reduce multiple hashes to a single hash in an efficient manner. This makes combining the hashes trivial.
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```
117+
private func computeHashes(_ value: T) -> [Int] {
118+
return randomSeeds.map() { seed in
119+
let hasher = Hasher()
120+
hasher.combine(seed)
121+
hasher.combine(value)
122+
let hashValue = hasher.finalize()
123+
return abs(hashValue % array.count)
124+
}
125+
}
126+
```
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If you want to learn more about this approach, you can read about the [Hasher documentation](https://developer.apple.com/documentation/swift/hasher) or Soroush Khanlou's [Swift 4.2 Bloom filter](http://khanlou.com/2018/09/bloom-filters/) implementation.
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*Written for Swift Algorithm Club by Jamil Dhanani. Edited by Matthijs Hollemans. Updated by Bruno Scheele.*

‎Bloom Filter/Tests/BloomFilterTests.swift

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func djb2(_ x: String) -> Int {
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var hash = 5381
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for char in x.characters {
9+
for char in x {
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hash = ((hash << 5) &+ hash) &+ char.hashValue
1111
}
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@@ -16,7 +16,7 @@ func djb2(_ x: String) -> Int {
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func sdbm(_ x: String) -> Int {
1717
var hash = 0
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19-
for char in x.characters {
19+
for char in x {
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hash = char.hashValue &+ (hash << 6) &+ (hash << 16) &- hash
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}
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