From dc62d25163c32bb76614d797dec6df5eb581d88d Mon Sep 17 00:00:00 2001
From: ladvoc <3182119+ladvoc@users.noreply.github.com>
Date: Sat, 14 Sep 2024 12:41:46 -0700
Subject: [PATCH] Implement discard conflicting initializer

---
 .../BijectiveDictionary+Initializers.swift        | 15 +++++++++++++++
 .../BijectiveDictionaryTests.swift                |  7 +++++++
 2 files changed, 22 insertions(+)

diff --git a/Sources/BijectiveDictionary/BijectiveDictionary+Initializers.swift b/Sources/BijectiveDictionary/BijectiveDictionary+Initializers.swift
index 118e6d6..0d8c0ac 100644
--- a/Sources/BijectiveDictionary/BijectiveDictionary+Initializers.swift
+++ b/Sources/BijectiveDictionary/BijectiveDictionary+Initializers.swift
@@ -44,6 +44,21 @@ extension BijectiveDictionary {
         self._rtl = Dictionary(uniqueKeysWithValues: reversePairs)
     }
     
+    /// Creates a new dictionary from the left-right pairs in the given sequence, discarding any conflicting pairs.
+    ///
+    /// - Parameter leftRightPairs: A sequence of left-right pairs to use for the new dictionary.
+    /// - Complexity: O(*n*), where *n* is the number of key-value pairs in the given sequence.
+    @inlinable public init<S>(
+        discardConflicting leftRightPairs: S
+    ) where S: Sequence, S.Element == Element {
+        self.init()
+        for pair in leftRightPairs where conflict(with: pair) == nil {
+            _ltr[pair.left] = pair.right
+            _rtl[pair.right] = pair.left
+        }
+        _invariantCheck()
+    }
+    
     /// Creates a bijective dictionary from a standard dictionary.
     ///
     /// Unlike a standard dictionary which only requires its keys be unique, a bijective
diff --git a/Tests/BijectiveDictionaryTests/BijectiveDictionaryTests.swift b/Tests/BijectiveDictionaryTests/BijectiveDictionaryTests.swift
index f856dbf..2e910f1 100644
--- a/Tests/BijectiveDictionaryTests/BijectiveDictionaryTests.swift
+++ b/Tests/BijectiveDictionaryTests/BijectiveDictionaryTests.swift
@@ -299,4 +299,11 @@ func conflict() {
     #expect(dict.conflict(with: ("A", 1)) == .pair)
     #expect(dict.conflict(with: ("A", 3)) == .both(otherLeft: "C", otherRight: 1))
 }
+
+@Test
+func discardConflicting() {
+    let pairs = [("A", 1), ("B", 1), ("A", 10), ("C", 4), ("C", 4), ("E", 5), ("A", 5)]
+    let dict = BijectiveDictionary(discardConflicting: pairs)
+    #expect(dict == ["A": 1, "C": 4, "E": 5])
+}
 #endif