Merge pull request #1379 from soobing/week5

[soobing] Week 05 Solutions

Author: soobing

encode-and-decode-strings/soobing.ts

@@ -0,0 +1,34 @@
+class Solution {
+  /**
+   * 문자열 배열을 하나의 문자열로 인코딩합니다.
+   * @param strs - 문자열 배열
+   * @returns 인코딩된 하나의 문자열
+   */
+  encode(strs: string[]): string {
+    return strs.map((str) => str.length + "#" + str).join("");
+  }
+
+  /**
+   * 인코딩된 문자열을 원래 문자열 배열로 디코딩합니다.
+   * @param str - 인코딩된 문자열
+   * @returns 디코딩된 문자열 배열
+   */
+  decode(str: string): string[] {
+    const result: string[] = [];
+
+    let i = 0;
+    while (i < str.length) {
+      let j = i;
+      while (str[j] !== "#") {
+        j++;
+      }
+
+      const length = parseInt(str.slice(i, j));
+      const word = str.slice(j + 1, j + 1 + length);
+      result.push(word);
+      i = j + 1 + length;
+    }
+
+    return result;
+  }
+}

group-anagrams/soobing.ts

@@ -0,0 +1,15 @@
+// idea: 배열에 담긴 모든 애들을 다 sorting하면서 sorting된 결과를 key로 바인딩하고 Record<string, string[]> 에 맞게 매핑하여 values들만 리턴하면 될것 같음
+function groupAnagrams(strs: string[]): string[][] {
+  const map = new Map<string, string[]>();
+
+  for (let i = 0; i < strs.length; i++) {
+    const key = strs[i].split("").sort().join("");
+    const group = map.get(key);
+    if (group) {
+      group.push(strs[i]);
+    } else {
+      map.set(key, [strs[i]]);
+    }
+  }
+  return [...map.values()];
+}

implement-trie-prefix-tree/soobing.ts

@@ -0,0 +1,46 @@
+class TrieNode {
+  children: Map<string, TrieNode>;
+  isEnd: boolean;
+
+  constructor() {
+    this.children = new Map();
+    this.isEnd = false;
+  }
+}
+
+class Trie {
+  root: TrieNode;
+
+  constructor() {
+    this.root = new TrieNode();
+  }
+
+  insert(word: string): void {
+    let node = this.root;
+    for (const char of word) {
+      if (!node.children.has(char)) {
+        node.children.set(char, new TrieNode());
+      }
+      node = node.children.get(char)!;
+    }
+    node.isEnd = true;
+  }
+
+  search(word: string): boolean {
+    const node = this._findNode(word);
+    return node !== null && node.isEnd;
+  }
+
+  startsWith(prefix: string): boolean {
+    return this._findNode(prefix) !== null;
+  }
+
+  private _findNode(word: string): TrieNode | null {
+    let node = this.root;
+    for (const char of word) {
+      if (!node.children.has(char)) return null;
+      node = node.children.get(char)!;
+    }
+    return node;
+  }
+}

word-break/soobing.ts

@@ -0,0 +1,15 @@
+function wordBreak(s: string, wordDict: string[]): boolean {
+  const dp = new Array(s.length + 1).fill(false);
+  dp[s.length] = true;
+
+  for (let i = s.length - 1; i >= 0; i--) {
+    for (const word of wordDict) {
+      if (i + word.length <= s.length && s.slice(i, i + word.length) === word) {
+        dp[i] = dp[i + word.length];
+      }
+
+      if (dp[i]) break;
+    }
+  }
+  return dp[0];
+}