[sukyoungshin] WEEK 05

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

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+function maxProfit(prices: number[]): number {
+  let minPrice = Number.MAX_SAFE_INTEGER;
+  let maxProfit = 0;
+
+  for (let i = 0; i < prices.length; i++) {
+    const currentPrice = prices[i];
+
+    if (currentPrice < minPrice) {
+      minPrice = currentPrice;
+    } else {
+      const profit = currentPrice - minPrice;
+      maxProfit = Math.max(maxProfit, profit);
+    }
+  }
+
+  return maxProfit;
+};
+
+maxProfit([7, 1, 5, 3, 6, 4]); // Output: 5
+maxProfit([7, 6, 4, 3, 1]); // Output: 0
+maxProfit([2, 4, 1]); // Output: 2
+maxProfit([1, 2]); // Output: 1
+maxProfit([2, 1]); // Output: 0
+maxProfit([1, 2, 3, 4, 5]); // Output: 4

encode-and-decode-strings/sukyoungshin.ts

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+// https://neetcode.io/problems/string-encode-and-decode
+
+class Solution {
+  /**
+   * @param {string[]} strs
+   * @returns {string}
+   */
+  encode(strs) {
+    let encodedStrings: string[] = [];
+
+    for (const word of strs) {
+      const length = word.length;
+      encodedStrings.push(`${length}#${word}`);
+    }
+
+    return encodedStrings.join("");
+  }
+
+  /**
+   * @param {string} str
+   * @returns {string[]}
+   */
+  decode(str) {
+    const decodedStrings: string[] = [];
+    let position = 0;
+
+    while (position < str.length) {
+      const hashIndex = str.indexOf("#", position);
+      const length = Number(str.slice(position, hashIndex));
+
+      const start = hashIndex + 1;
+      const end = start + length;
+      const word = str.slice(start, end);
+      decodedStrings.push(word);
+
+      position = end;
+    }
+
+    return decodedStrings;
+  }
+};

group-anagrams/sukyoungshin.ts

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+// 1. 객체사용
+function groupAnagrams1(strs: string[]): string[][] {
+  let anagramGroups: Record<string, string[]> = {};
+  for (const word of strs) {
+    const sortedKey = [...word].sort().join("");
+
+    if (sortedKey in anagramGroups) {
+      anagramGroups[sortedKey].push(word);
+    } else {
+      anagramGroups[sortedKey] = [word];
+    }
+  }
+
+  return Object.values(anagramGroups);
+};
+
+// 2. Map 사용
+function groupAnagrams2(strs: string[]): string[][] {
+  let anagramGroups = new Map<string, string[]>();
+  for (const word of strs) {
+    const key = [...word].sort().join("");
+
+    if (anagramGroups.has(key)) {
+      anagramGroups.get(key)?.push(word);
+    } else {
+      anagramGroups.set(key, [word]);
+    }
+  }
+
+  return [...anagramGroups.values()];
+};

word-break/sukyoungshin.ts

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+function wordBreak(s: string, wordDict: string[]): boolean {
+  const cache: Record<string, boolean> = {};
+
+  function canSplit(str: string): boolean {
+    if (str === "") return true;
+    if (cache[str] !== undefined) return cache[str];
+
+    for (let i = 1; i <= str.length; i++) {
+      const left = str.slice(0, i);
+      const right = str.slice(i);
+
+      if (wordDict.includes(left) && canSplit(right)) {
+        cache[str] = true;
+        return true;
+      }
+    }
+
+    cache[str] = false;
+    return false;
+  }
+
+  return canSplit(s);
+};