0737-sentence-similarity-ii

Author: bofeizhu

0737-sentence-similarity-ii.playground/Contents.swift

@@ -0,0 +1,107 @@
+/// 737. Sentence Similarity II
+/// Given two sentences words1, words2 (each represented as an array of strings), and a list of
+/// similar word pairs pairs, determine if two sentences are similar.
+///
+/// For example, words1 = ["great", "acting", "skills"] and words2 = ["fine", "drama", "talent"] are
+/// similar, if the similar word pairs are pairs = [["great", "good"], ["fine", "good"],
+/// ["acting","drama"], ["skills","talent"]].
+/// Note that the similarity relation is transitive. For example, if "great" and "good" are similar,
+/// and "fine" and "good" are similar, then "great" and "fine" are similar. Similarity is also
+/// symmetric. For example, "great" and "fine" being similar is the same as "fine" and "great" being
+/// similar.
+/// Also, a word is always similar with itself. For example, the sentences words1 = ["great"],
+/// words2 = ["great"], pairs = [] are similar, even though there are no specified similar word
+/// pairs.
+/// Finally, sentences can only be similar if they have the same number of words. So a sentence like
+/// words1 = ["great"] can never be similar to words2 = ["doubleplus","good"].
+
+import XCTest
+
+struct UnionFind<T: Hashable> {
+    private var index: [T: Int] = [:]
+    private var parent: [Int] = []
+    private var size: [Int] = []
+    
+    mutating func addSetWith(_ element: T) {
+        index[element] = parent.count
+        parent.append(parent.count)
+        size.append(1)
+    }
+    
+    /// Path Compression.
+    private mutating func setByIndex(_ index: Int) -> Int {
+        if index != parent[index] {
+            parent[index] = setByIndex(parent[index])
+        }
+        return parent[index]
+    }
+    
+    mutating func setOf(_ element: T) -> Int? {
+        if let indexOfElement = index[element] {
+            return setByIndex(indexOfElement)
+        } else {
+            return nil
+        }
+    }
+    
+    mutating func unionSetsContaining(_ firstElement: T, and secondElement: T) {
+        if let firstSet = setOf(firstElement), let secondSet = setOf(secondElement) {
+            if firstSet != secondSet {
+                if size[firstSet] < size[secondSet] {
+                    parent[firstSet] = secondSet
+                    size[secondSet] += size[firstSet]
+                } else {
+                    parent[secondSet] = firstSet
+                    size[firstSet] += size[secondSet]
+                }
+            }
+        }
+    }
+    
+    mutating func inSameSet(_ firstElement: T, and secondElement: T) -> Bool {
+        if let firstSet = setOf(firstElement), let secondSet = setOf(secondElement) {
+            return firstSet == secondSet
+        } else {
+            return false
+        }
+    }
+}
+
+/// Approach: Union Find
+func areSentencesSimilarTwo(_ words1: [String], _ words2: [String], _ pairs: [[String]]) -> Bool {
+    guard words1.count == words2.count else { return false }
+    var dset = UnionFind<String>()
+    for p in pairs {
+        let word1 = p[0]
+        let word2 = p[1]
+        if dset.setOf(word1) == nil {
+            dset.addSetWith(word1)
+        }
+        if dset.setOf(word2) == nil {
+            dset.addSetWith(word2)
+        }
+        dset.unionSetsContaining(word1, and: word2)
+    }
+    for i in 0..<words1.count {
+        if !dset.inSameSet(words1[i], and: words2[i]) {
+            return false
+        }
+    }
+    return true
+}
+
+class Tests: XCTestCase {
+    func testExample() {
+        let words1 = ["great", "acting", "skills"]
+        let words2 = ["fine", "drama", "talent"]
+        let pairs = [
+            ["great", "good"],
+            ["fine", "good"],
+            ["drama", "acting"],
+            ["skills", "talent"],
+        ]
+        XCTAssertTrue(areSentencesSimilarTwo(words1, words2, pairs))
+    }
+}
+
+Tests.defaultTestSuite.run()

0737-sentence-similarity-ii.playground/contents.xcplayground

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+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='macos' executeOnSourceChanges='false'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>

README.md

@@ -64,6 +64,7 @@ You can visit the pages below to search problems by company tags. Then come back
 681 | [Next Closest Time](https://leetcode.com/problems/next-closest-time/description/) | [Solution](https://github.com/zhubofei/LeetCode-Swift/blob/master/0681-next-closest-time.playground/Contents.swift) | Simulation
 683 | [K Empty Slots](https://leetcode.com/problems/k-empty-slots/description/) | [Solution](https://github.com/zhubofei/LeetCode-Swift/blob/master/0683-k-empty-slots.playground/Contents.swift) | Sliding Window
 686 | [Repeated String Match](https://leetcode.com/problems/repeated-string-match/description/) | [Solution](https://github.com/zhubofei/LeetCode-Swift/blob/master/0686-repeated-string-match.playground/Contents.swift) | String
+737 | [Sentence Similarity II \*](https://leetcode.com/problems/sentence-similarity-ii/description/) | [Solution](https://github.com/zhubofei/LeetCode-Swift/blob/master/0737-sentence-similarity-ii.playground/Contents.swift) | Union Find
 843 | [Guess the Word \*](https://leetcode.com/problems/guess-the-word/description/) | [Solution](https://github.com/zhubofei/LeetCode-Swift/blob/master/0843-guess-the-word.playground/Contents.swift) | Minimax
 
 **\* problems are not compilable on LeetCode. I have filed bug report for these problems.**