[hsskey] Week 05 Solutions

best-time-to-buy-and-sell-stock/hsskey.js

@@ -0,0 +1,19 @@
+/**
+ * @param {number[]} prices
+ * @return {number}
+ */
+var maxProfit = function(prices) {
+    let buy = prices[0]
+    let maxVal = 0
+
+    for(let i = 1; i < prices.length; i++) {
+        if(prices[i - 1] > prices[i]) {
+            buy = Math.min(buy, prices[i])
+        }
+
+        if(prices[i - 1] < prices[i]) {
+            maxVal = Math.max(maxVal, prices[i] - buy)
+        }
+    }
+    return maxVal
+};

encode-and-decode-strings/hsskey.js

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+class Solution {
+    /**
+     * @param {string[]} strs
+     * @returns {string}
+     */
+    encode(strs) {
+        return strs.map((item) => `${item.length}#${item}`).join('');
+    }
+
+    /**
+     * @param {string} str
+     * @returns {string[]}
+     */
+    decode(str) {
+        const result = [];
+        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/hsskey.js

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+/**
+ * @param {string[]} strs
+ * @return {string[][]}
+ */
+var groupAnagrams = function(strs) {
+    const map = new Map()
+
+    for(const str of strs) {
+        const sortedStr = [...str].sort().join('')
+        if(map.has(sortedStr)) {
+            map.get(sortedStr).push(str)
+        } else {
+            map.set(sortedStr, [str])
+        }
+    }
+
+    return Array.from(map.values())
+};

implement-trie-prefix-tree/hsskey.js

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+class TrieNode {
+    constructor() {
+        this.children = {};
+        this.isEndOfWord = false;
+    }
+}
+
+var Trie = function() {
+    this.root = new TrieNode();
+};
+
+/** 
+ * @param {string} word
+ * @return {void}
+ */
+Trie.prototype.insert = function(word) {
+    let node = this.root;
+    for (const char of word) {
+        if (!node.children[char]) {
+            node.children[char] = new TrieNode();
+        }
+        node = node.children[char];
+    }
+    node.isEndOfWord = true;
+};
+
+/** 
+ * @param {string} word
+ * @return {boolean}
+ */
+Trie.prototype.search = function(word) {
+    let node = this.root;
+    for (const char of word) {
+        if (!node.children[char]) return false;
+        node = node.children[char];
+    }
+    return node.isEndOfWord;
+};
+
+/** 
+ * @param {string} prefix
+ * @return {boolean}
+ */
+Trie.prototype.startsWith = function(prefix) {
+    let node = this.root;
+    for (const char of prefix) {
+        if (!node.children[char]) return false;
+        node = node.children[char];
+    }
+    return true;
+};

word-break/hsskey.js

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+/**
+ * @param {string} s
+ * @param {string[]} wordDict
+ * @return {boolean}
+ */
+var wordBreak = function(s, wordDict) {
+    const wordSet = new Set(wordDict);
+    const dp = new Array(s.length + 1).fill(false);
+    dp[0] = true;
+
+    for (let i = 1; i <= s.length; i++) {
+        for (let j = 0; j < i; j++) {
+            const word = s.slice(j, i);
+            if (dp[j] && wordSet.has(word)) {
+                dp[i] = true;
+                break;
+            }
+        }
+    }
+
+    return dp[s.length];
+};