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Binary search. if -> guard #994

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Binary search. if -> guard #994

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b41b80d
Update BinarySearch.swift
Mar 12, 2022
d50d175
Merge pull request #1 from prokhorovxo/prokhorovxo-patch-1
Mar 12, 2022
1091db5
Update README.markdown
Mar 12, 2022
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18 changes: 9 additions & 9 deletions Binary Search/BinarySearch.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -14,17 +14,17 @@ import Foundation
// The recursive version of binary search.

public func binarySearch<T: Comparable>(_ a: [T], key: T, range: Range<Int>) -> Int? {
if range.lowerBound >= range.upperBound {
guard range.lowerBound < range.upperBound else {
return nil
}

let midIndex = range.lowerBound + (range.upperBound - range.lowerBound) / 2
if a[midIndex] > key {
return binarySearch(a, key: key, range: range.lowerBound ..< midIndex)
} else if a[midIndex] < key {
return binarySearch(a, key: key, range: midIndex + 1 ..< range.upperBound)
} else {
let midIndex = range.lowerBound + (range.upperBound - range.lowerBound) / 2
if a[midIndex] > key {
return binarySearch(a, key: key, range: range.lowerBound ..< midIndex)
} else if a[midIndex] < key {
return binarySearch(a, key: key, range: midIndex + 1 ..< range.upperBound)
} else {
return midIndex
}
return midIndex
}
}

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27 changes: 9 additions & 18 deletions Binary Search/README.markdown
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Expand Up @@ -58,26 +58,17 @@ Here is a recursive implementation of binary search in Swift:

```swift
func binarySearch<T: Comparable>(_ a: [T], key: T, range: Range<Int>) -> Int? {
if range.lowerBound >= range.upperBound {
// If we get here, then the search key is not present in the array.
guard range.lowerBound < range.upperBound else {
return nil

}

let midIndex = range.lowerBound + (range.upperBound - range.lowerBound) / 2
if a[midIndex] > key {
return binarySearch(a, key: key, range: range.lowerBound ..< midIndex)
} else if a[midIndex] < key {
return binarySearch(a, key: key, range: midIndex + 1 ..< range.upperBound)
} else {
// Calculate where to split the array.
let midIndex = range.lowerBound + (range.upperBound - range.lowerBound) / 2

// Is the search key in the left half?
if a[midIndex] > key {
return binarySearch(a, key: key, range: range.lowerBound ..< midIndex)

// Is the search key in the right half?
} else if a[midIndex] < key {
return binarySearch(a, key: key, range: midIndex + 1 ..< range.upperBound)

// If we get here, then we've found the search key!
} else {
return midIndex
}
return midIndex
}
}
```
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