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Implemented 'Longest Word in Dictionary through Deleting' challenge
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68 changes: 68 additions & 0 deletions
68
LeetCode/LeetCode/Challenges/LongestWordInDictionaryThroughDeleting.swift
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,68 @@ | ||
| // | ||
| // LongestWordInDictionaryThroughDeleting.swift | ||
| // LeetCode | ||
| // | ||
| // Created by William Boles on 05/09/2024. | ||
| // | ||
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| import Foundation | ||
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| //https://leetcode.com/problems/longest-word-in-dictionary-through-deleting/ | ||
| struct LongestWordInDictionaryThroughDeleting { | ||
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| //Time: O(n * m)) where n is the number of words in `dictionary` | ||
| // where m is the number of characters in a word | ||
| //Space: O(m + s) where m is the number of characters in a word | ||
| // where s is the number of characters in `s` | ||
| //array | ||
| //string | ||
| //two pointers | ||
| //fast forward | ||
| //subsequence | ||
| // | ||
| //Solution Description: | ||
| //Iterating through the elements in `dictionary` we attempt to see if that element could be a subsequence of `s`. A | ||
| //subsequence is a non-contiguous slice of an array i.e. while order is preserved some characters can be skipped over. We | ||
| //use two pointers to iterate through `word` and `s` to determine if `word` is a subsequence of `s`. If `word` is a | ||
| //subsequence of `s` we compare `word` against `longestWord` using a two tier approach: first we check length then if | ||
| //`longestWord` and `word` have the same length we check lexicographical ordering. If `word` is either longer or of equal | ||
| //length with a smaller lexicographical order then we set it as `longestWord`. We repeat this process for all elements in | ||
| //`dictionary`. Once all elements have been checked we return `longestWord`. | ||
| func findLongestWord(_ s: String, _ dictionary: [String]) -> String { | ||
| var longestWord = "" | ||
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| for word in dictionary { | ||
| guard word.count <= s.count else { //`word` can't be longer than `s` | ||
| continue | ||
| } | ||
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| if isSubsequence(word, of: s) { | ||
| if (word.count > longestWord.count) || // longer word? | ||
| ((word.count == longestWord.count) && (word < longestWord)) { //same length but lexicographical smaller? | ||
| longestWord = word | ||
| } | ||
| } | ||
| } | ||
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| return longestWord | ||
| } | ||
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| private func isSubsequence(_ a: String, of b: String) -> Bool { | ||
| let a = Array(a) | ||
| let b = Array(b) | ||
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| var p1 = 0 | ||
| var p2 = 0 | ||
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| while p1 < a.count { | ||
| while p2 < b.count, a[p1] != b[p2] { //fast forward | ||
| p2 += 1 | ||
| } | ||
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| p1 += 1 | ||
| p2 += 1 | ||
| } | ||
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| return p2 <= b.count | ||
| } | ||
| } |
51 changes: 51 additions & 0 deletions
51
LeetCode/LeetCodeTests/Tests/LongestWordInDictionaryThroughDeletingTests.swift
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,51 @@ | ||
| // | ||
| // LongestWordInDictionaryThroughDeletingTests.swift | ||
| // LeetCodeTests | ||
| // | ||
| // Created by William Boles on 05/09/2024. | ||
| // | ||
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| import XCTest | ||
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| @testable import LeetCode | ||
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| final class LongestWordInDictionaryThroughDeletingTests: XCTestCase { | ||
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| // MARK: - Tests | ||
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| func test_A() { | ||
| let s = "abpcplea" | ||
| let dictionary = ["ale","apple","monkey","plea"] | ||
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| let result = LongestWordInDictionaryThroughDeleting().findLongestWord(s, dictionary) | ||
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| XCTAssertEqual(result, "apple") | ||
| } | ||
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| func test_B() { | ||
| let s = "abpcplea" | ||
| let dictionary = ["a","b","c"] | ||
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| let result = LongestWordInDictionaryThroughDeleting().findLongestWord(s, dictionary) | ||
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| XCTAssertEqual(result, "a") | ||
| } | ||
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| func test_C() { | ||
| let s = "abpcplea" | ||
| let dictionary = ["b","c","a"] | ||
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| let result = LongestWordInDictionaryThroughDeleting().findLongestWord(s, dictionary) | ||
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| XCTAssertEqual(result, "a") | ||
| } | ||
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| func test_D() { | ||
| let s = "abpcplea" | ||
| let dictionary = ["ale","apple","monkey","plea", "abpcplaaa","abpcllllll","abccclllpppeeaaaa"] | ||
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| let result = LongestWordInDictionaryThroughDeleting().findLongestWord(s, dictionary) | ||
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| XCTAssertEqual(result, "apple") | ||
| } | ||
| } |