[JustHm] Week 05 Solution

best-time-to-buy-and-sell-stock/JustHm.swift

@@ -0,0 +1,17 @@
+// time: O(n) space: O(n)
+class Solution {
+    func maxProfit(_ prices: [Int]) -> Int {
+        guard !prices.isEmpty else { return 0 }
+        var result = [Int]()
+        var current = prices[0]
+
+        for price in prices {
+            if current > price {
+                current = price
+                continue
+            }
+            result.append(price - current)
+        }
+        return result.max() ?? 0
+    }
+}

implement-trie-prefix-tree/JustHm.swift

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+
+class Trie {
+    var children: [Character: Trie] = [:]
+    var isEndOfWord = false
+
+    func insert(_ word: String) {
+        guard !word.isEmpty else { return }
+        var node = self
+        for char in word {
+            if node.children[char] == nil {
+                node.children[char] = Trie()
+            }
+            node = node.children[char]!
+        }
+        node.isEndOfWord = true
+    }
+
+    func search(_ word: String) -> Bool {
+        guard let node = findNode(word) else { return false }
+        return node.isEndOfWord
+    }
+
+    func startsWith(_ prefix: String) -> Bool {
+        return findNode(prefix) != nil
+    }
+
+    private func findNode(_ word: String) -> Trie? {
+        var node = self
+        for char in word {
+            guard let next = node.children[char] else { return nil }
+            node = next
+        }
+        return node
+    }
+}