[sadie100] WEEK7 Solutions

design-add-and-search-words-data-structure/sadie100.ts

@@ -0,0 +1,72 @@
+/*
+words를 맵형태로 저장, 각 스펠링과 다음에 나오는 문자열을 key-value로 하는 맵으로 저장
+.의 경우 모든 경우를 탐색한다
+
+시간복잡도 :
+    addWord : O(L) (L은 words의 길이)
+    search : 일반적으로 O(L), .이 많으면 O(26^k) (k는 .의 개수)
+
+*/
+class TrieNode {
+  children: Map<string, TrieNode>
+  isEnd: boolean
+
+  constructor() {
+    this.children = new Map()
+    this.isEnd = false
+  }
+}
+
+class WordDictionary {
+  words = new TrieNode()
+  constructor() {}
+
+  addWord(word: string): void {
+    let curWords = this.words
+
+    for (let i = 0; i < word.length; i++) {
+      const char = word[i]
+
+      if (!curWords.children.has(char)) {
+        curWords.children.set(char, new TrieNode())
+      }
+
+      curWords = curWords.children.get(char)
+    }
+    curWords.isEnd = true
+  }
+
+  search(word: string): boolean {
+    return this.searchRecursively(word, this.words)
+  }
+
+  searchRecursively(word: string, area: TrieNode) {
+    for (let i = 0; i < word.length; i++) {
+      if (!area) return false
+      const char = word[i]
+
+      if (char === '.') {
+        const values = [...area.children.values()]
+
+        for (let newArea of values) {
+          const result = this.searchRecursively(word.slice(i + 1), newArea)
+          if (result) return true
+        }
+        return false
+      } else {
+        if (!area.children.has(char)) return false
+        area = area.children.get(char)
+      }
+    }
+
+    if (area.isEnd) return true
+    return false
+  }
+}
+
+/**
+ * Your WordDictionary object will be instantiated and called as such:
+ * var obj = new WordDictionary()
+ * obj.addWord(word)
+ * var param_2 = obj.search(word)
+ */

reverse-linked-list/sadie100.ts

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+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     val: number
+ *     next: ListNode | null
+ *     constructor(val?: number, next?: ListNode | null) {
+ *         this.val = (val===undefined ? 0 : val)
+ *         this.next = (next===undefined ? null : next)
+ *     }
+ * }
+ */
+
+/*
+직전 노드를 담는 변수 before과 다음 노드를 담는 변수 next, 순회중인 노드 head 변수와 함께 list를 순회
+head의 next에 before을 넣고, head를 next로 변환하며 head가 null이 아닐 때까지 반복한다
+
+시간복잡도 : O(N) - 1번 순회
+공간복잡도 : O(1) - before, next 변수
+
+*/
+function reverseList(head: ListNode | null): ListNode | null {
+  if (!head) return head
+  let originNext = head.next
+  let before = null
+
+  while (head !== null) {
+    originNext = head.next
+    head.next = before
+    before = head
+    head = originNext
+  }
+
+  return before
+}