[casentino] WEEK 05 solutions

[casentino] WEEK 05 solutions

Author: casentino

best-time-to-buy-and-sell-stock/casentino.ts

@@ -0,0 +1,11 @@
+function maxProfit(prices: number[]): number {
+  const dp = new Array(prices.length).fill(0);
+  dp[0] = 0;
+  let maxProfit = 0;
+  for (let i = 1; i < prices.length; i++) {
+    dp[i] = Math.max(prices[i] - prices[i - 1], prices[i] - prices[i - 1] + dp[i - 1]);
+
+    maxProfit = Math.max(dp[i], maxProfit);
+  }
+  return maxProfit;
+}

group-anagrams/casentino.ts

@@ -0,0 +1,13 @@
+function groupAnagrams(strs: string[]): string[][] {
+  const hashMap = new Map();
+  for (let i = 0; i < strs.length; i++) {
+    const key = Array.from(strs[i]).sort().join("");
+
+    if (!hashMap.has(key)) {
+      hashMap.set(key, [strs[i]]);
+    } else {
+      hashMap.get(key).push(strs[i]);
+    }
+  }
+  return Array.from(hashMap.values());
+}

implement-trie-prefix-tree/casentino.ts

@@ -0,0 +1,55 @@
+type ChildTrie = {
+  value?: string;
+  isEnd?: boolean;
+  childrens: ChildrenMap;
+};
+type ChildrenMap = {
+  [key: string]: ChildTrie;
+};
+
+class Trie {
+  childrens: ChildrenMap = {};
+  constructor() {}
+
+  insert(word: string): void {
+    if (word.length === 0) {
+      return;
+    }
+    let current: ChildTrie = {
+      childrens: this.childrens,
+    };
+    for (let i = 0; i < word.length; i++) {
+      if (current.childrens[word[i]] === undefined) {
+        current.childrens[word[i]] = { value: word[i], isEnd: false, childrens: {} };
+      }
+
+      current = current.childrens[word[i]];
+    }
+    current.isEnd = true;
+  }
+
+  search(word: string): boolean {
+    let current: ChildTrie = {
+      childrens: this.childrens,
+    };
+    for (let i = 0; i < word.length; i++) {
+      if (current.childrens[word[i]] === undefined) {
+        return false;
+      }
+
+      current = current.childrens[word[i]];
+    }
+    return current.isEnd ?? false;
+  }
+
+  startsWith(prefix: string): boolean {
+    let current = this.childrens;
+    for (let i = 0; i < prefix.length; i++) {
+      if (current[prefix[i]] === undefined) {
+        return false;
+      }
+      current = current[prefix[i]].childrens;
+    }
+    return true;
+  }
+}

word-break/casentino.ts

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