From 514dc4ef0c8782ac4912e84e97222961af4f194d Mon Sep 17 00:00:00 2001
From: mcekr <>
Date: Thu, 8 Oct 2020 18:57:53 +0800
Subject: [PATCH 1/3] Add isSorted

---
 Sources/Algorithms/isSorted.swift | 42 +++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)
 create mode 100644 Sources/Algorithms/isSorted.swift

diff --git a/Sources/Algorithms/isSorted.swift b/Sources/Algorithms/isSorted.swift
new file mode 100644
index 00000000..e7182cef
--- /dev/null
+++ b/Sources/Algorithms/isSorted.swift
@@ -0,0 +1,42 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift Algorithms open source project
+//
+// Copyright (c) 2020 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
+//===----------------------------------------------------------------------===//
+// isSorted()
+//===----------------------------------------------------------------------===//
+
+
+extension Sequence where Element: Comparable {
+    public func isSorted() -> Bool {
+        /// Returns Bool, indicating whether a sequence is sorted
+        /// into non-descending order.
+        ///
+        /// - Complexity: O(*n*), where *n* is the length of the sequence.
+        
+        isSorted(by: <)
+    }
+    
+    public func isSorted(by areInIncreasingOrder: (Element, Element) -> Bool) -> Bool {
+        /// Returns Bool, indicating whether a sequence is sorted using
+        /// the given predicate as the comparison between elements.
+        ///
+        /// - Complexity: O(*n*), where *n* is the length of the sequence.
+        
+        var prev: Element?
+        for element in self {
+            if let p = prev, !areInIncreasingOrder(p, element) {
+                return false
+            }
+            prev = element
+        }
+        return true
+    }
+}

From 0807ed02b0cc49c1c361443001a9cf9fe25a80f9 Mon Sep 17 00:00:00 2001
From: mcekr <>
Date: Thu, 8 Oct 2020 19:20:33 +0800
Subject: [PATCH 2/3] Add IsSortedTests

---
 .../SwiftAlgorithmsTests/IsSortedTests.swift  | 25 +++++++++++++++++++
 1 file changed, 25 insertions(+)
 create mode 100644 Tests/SwiftAlgorithmsTests/IsSortedTests.swift

diff --git a/Tests/SwiftAlgorithmsTests/IsSortedTests.swift b/Tests/SwiftAlgorithmsTests/IsSortedTests.swift
new file mode 100644
index 00000000..ba808089
--- /dev/null
+++ b/Tests/SwiftAlgorithmsTests/IsSortedTests.swift
@@ -0,0 +1,25 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift Algorithms open source project
+//
+// Copyright (c) 2020 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
+import XCTest
+import Algorithms
+
+final class IsSortedTests: XCTestCase {
+    
+  func testIsSorted() {
+    let a = 0...10
+    let b = (0...10).reversed()
+    let c = Array(repeating: 42, count: 10)
+    XCTAssertTrue(a.isSorted())
+    XCTAssertTrue(b.isSorted(by: >))
+    XCTAssertTrue(c.allEqual())
+  }
+}

From a226cb982f2901dd0f600b3ead4c99e4ac55f67d Mon Sep 17 00:00:00 2001
From: mcekr <>
Date: Thu, 8 Oct 2020 19:23:06 +0800
Subject: [PATCH 3/3] Add allEqual

---
 Sources/Algorithms/isSorted.swift | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/Sources/Algorithms/isSorted.swift b/Sources/Algorithms/isSorted.swift
index e7182cef..55e70ce8 100644
--- a/Sources/Algorithms/isSorted.swift
+++ b/Sources/Algorithms/isSorted.swift
@@ -39,4 +39,13 @@ extension Sequence where Element: Comparable {
         }
         return true
     }
+    
+    public func allEqual() -> Bool {
+        /// Returns Bool, indicating whether all the
+        /// elements in sequence are equal to each other.
+        ///
+        /// - Complexity: O(*n*), where *n* is the length of the sequence.
+
+        isSorted(by: ==)
+    }
 }