Hash Table

Author: HuXn-WebDev

6. Hash Table/1. Custom Hash Table/index.js

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+class HashTable {
+  constructor(size = 6) {
+    this.keyMap = new Array(size);
+  }
+
+  _hashFunction(key) {
+    let sum = 0;
+    const PRIME_NUMBER = 31;
+
+    for (let i = 0; i < Math.min(key.length, 100); i++) {
+      const charCode = key.charCodeAt(0) - 96;
+      sum = (sum * PRIME_NUMBER + charCode) % this.keyMap.length;
+    }
+
+    return sum;
+  }
+
+  set(key, value) {
+    const index = this._hashFunction(key);
+    if (!this.keyMap[index]) this.keyMap[index] = [];
+    this.keyMap[index].push([key, value]);
+    return this;
+  }
+
+  get(key) {
+    const index = this._hashFunction(key);
+    if (this.keyMap[index]) {
+      for (let i = 0; i < this.keyMap[index].length; i++) {
+        if (this.keyMap[index][i][0] === key) {
+          return this.keyMap[index][i][1];
+        }
+      }
+    }
+    return undefined;
+  }
+
+  getAllKeys() {
+    const keys = [];
+    for (let i = 0; i < this.keyMap.length; i++) {
+      if (this.keyMap[i]) {
+        for (let j = 0; j < this.keyMap[i].length; j++) {
+          keys.push(this.keyMap[i][j][0]);
+        }
+      }
+    }
+    return keys;
+  }
+
+  getAllValues() {
+    const values = [];
+    for (let i = 0; i < this.keyMap.length; i++) {
+      if (this.keyMap[i]) {
+        for (let j = 0; j < this.keyMap[i].length; j++) {
+          values.push(this.keyMap[i][j][1]);
+        }
+      }
+    }
+    return values;
+  }
+}
+
+const phoneBook = new HashTable();
+phoneBook.set("john", "555-333-444");
+phoneBook.set("jordan", "222-444-666");
+phoneBook.set("michel", "111-666-222");
+console.log(phoneBook.get("jordan"));
+console.log(phoneBook.getAllValues());
+console.log(phoneBook.getAllKeys());

6. Hash Table/2. Challenges/1. Word Instance Counter/index.js

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+function wordCounter(text) {
+  const lowerText = text.toLowerCase();
+  const wordMap = {};
+  const words = lowerText.split(/\s+/);
+
+  for (const word of words) {
+    if (word in wordMap) {
+      wordMap[word]++;
+    } else {
+      wordMap[word] = 1;
+    }
+  }
+
+  return wordMap;
+}
+
+const text = "Hello my name name name is huxn";
+// { hello: 1, my: 1, name: 3, is: 1, huxn: 1 }
+const wordCounts = wordCounter(text);
+
+console.log(wordCounts);

6. Hash Table/2. Challenges/2. Two Sum/index.js

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+function twoSum(nums, target) {
+  const numMap = {};
+
+  for (let i = 0; i < nums.length; i++) {
+    const complement = target - nums[i];
+    if (complement in numMap && numMap[complement] !== i) {
+      return [numMap[complement], i];
+    }
+    numMap[nums[i]] = i;
+  }
+
+  return [];
+}
+
+const nums = [2, 7, 11, 15];
+const target = 9;
+const result = twoSum(nums, target);
+console.log(result); // [0, 1]

6. Hash Table/2. Challenges/3. Group Anagrams/index.js

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+function groupAnagrams(strs) {
+  const anagramMap = {};
+
+  for (const str of strs) {
+    const sortedStr = str.split("").sort().join("");
+
+    if (sortedStr in anagramMap) {
+      anagramMap[sortedStr].push(str);
+    } else {
+      anagramMap[sortedStr] = [str];
+    }
+  }
+
+  return Object.values(anagramMap);
+}
+
+const strs = ["eat", "tea", "tan", "ate", "nat", "bat"];
+const groups = groupAnagrams(strs);
+
+console.log(groups);
+// Output: [["eat", "tea", "ate"], ["bat"], ["nat", "tan"]]