Arrays Complete Course

Author: HuXn-WebDev

3. Arrays/1. Intro/index.js

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+const stringArr = ["a", "b", "c", "d"];
+const numArr = [1, 2, 3, 4, 5];
+const boolArr = [true, false];
+const mixed = ["a", 2, true, undefined, null, { a: "a" }, ["b"]];
+console.log(mixed);

3. Arrays/2. Custom Array/index.js

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+class MyArray {
+  constructor() {
+    this.length = 0;
+    this.data = {};
+  }
+
+  push(item) {
+    this.data[this.length] = item;
+    this.length++;
+    return this.length;
+  }
+
+  get(index) {
+    return this.data[index];
+  }
+
+  pop() {
+    const lastItem = this.data[this.length - 1];
+    delete this.data[this.length - 1];
+    this.length--;
+    return lastItem;
+  }
+
+  shift() {
+    const firstItem = this.data[0];
+
+    for (let i = 0; i < this.length; i++) {
+      this.data[i] = this.data[i + 1];
+    }
+
+    // Delete the last element (which now contains the original second element)
+    delete this.data[this.length - 1];
+    this.length--;
+
+    // Return the first item that was removed from the array
+    return firstItem;
+  }
+
+  delete(index) {
+    // Store the item to be removed
+    const item = this.data[index];
+
+    // Shift elements after the target element (excluding the last one)
+    for (let i = index; i < this.length - 1; i++) {
+      this.data[i] = this.data[i + 1];
+    }
+
+    // Delete the last element (which now holds the element to be removed)
+    delete this.data[this.length - 1];
+
+    // Decrement length
+    this.length--;
+
+    // Return the removed item
+    return item;
+  }
+}
+
+const myNewArray = new MyArray();
+myNewArray.push("one");
+myNewArray.push("two");
+myNewArray.push("three");
+// myNewArray.pop();
+// myNewArray.shift();
+myNewArray.delete(1);
+// console.log(myNewArray.get(0));
+console.log(myNewArray);

3. Arrays/3. Challenges/1. Reverse String.js

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+// 1. Convert string to array (split method)
+// 2. Reverse the array (reverse method)
+// 3. Convert array back to string (join method)
+
+const reverseString = (str) => str.split("").reverse().join("");
+console.log(reverseString("hello"));

3. Arrays/3. Challenges/2. Palindromes.js

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+// 1. Convert string to array (split method)
+// 2. Reverse the array (reverse method)
+// 3. Convert array back to string (join method)
+// 4. Compare strings
+
+const palindrome = (str) => str.split("").reverse().join("") === str;
+
+console.log(palindrome("cddc"));
+console.log(palindrome("Hello"));

3. Arrays/3. Challenges/3. Integer Reversal.js

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+// 1. Convert number to string (toString method)
+// 2. Convert String to array (split method)
+// 3. Reverse the string (reverse method)
+// 4. Convert array back to string (join method)
+// 5. Convert string to number (parseInt method)
+// 6. Return the number
+
+const reverseInt = (n) => {
+  const reversed = n.toString().split("").reverse().join("");
+  return parseInt(reversed) * Math.sign(n);
+};
+
+console.log(reverseInt(-123));

3. Arrays/3. Challenges/4. Sentence Capitalization.js

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+// 1. Make the string lowercase (toLowerCase method)
+// 2. Convert string to array (split method)
+// 3. Capitalize each word (map method)
+// 3. Convert array back to string (join method)
+
+const capitalize = (str) => {
+  return str
+    .toLowerCase()
+    .split(" ")
+    .map((word) => word[0].toUpperCase() + word.slice(1))
+    .join(" ");
+};
+
+console.log(capitalize("hello world"));
+console.log(capitalize("jordan peterson"));

3. Arrays/3. Challenges/5. FizzBuzz.js

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+// 1. Print numbers from 1 to n
+// 2. If number is divisible by 3, print "Fizz"
+// 3. If number is divisible by 5, print "Buzz"
+// 4. If number is divisible by 3 and 5, print "FizzBuzz"
+// 5. Else, print the number
+
+const fizzBuzz = (n) => {
+  for (let i = 1; i <= n; i++) {
+    if (i % 3 === 0 && i % 5 === 0) {
+      console.log("FizzBuzz");
+    } else if (i % 3 === 0) {
+      console.log("Fizz");
+    } else if (i % 5 === 0) {
+      console.log("Buzz");
+    } else {
+      console.log(i);
+    }
+  }
+};
+
+fizzBuzz(15);

3. Arrays/3. Challenges/6. MaxProfit.js

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+const maxProfit = (prices) => {
+  let minPrice = prices[0]; // Assume the first day is the cheapest to buy
+  let maxProfit = 0;
+
+  for (let i = 1; i < prices.length; i++) {
+    const currentPrice = prices[i];
+    // console.log(currentPrice);
+
+    // Update minimum price if a lower price is found
+    minPrice = Math.min(minPrice, currentPrice);
+    // console.log(minPrice);
+
+    // Calculate potential profit for selling today
+    const potentialProfit = currentPrice - minPrice;
+    // console.log(potentialProfit);
+
+    // Update maxProfit if a higher profit is found
+    maxProfit = Math.max(maxProfit, potentialProfit);
+    // console.log(maxProfit);
+  }
+
+  return maxProfit;
+};
+
+const prices = [7, 1, 5, 3, 6, 4];
+const profit = maxProfit(prices);
+console.log("Maximum profit:", profit);

3. Arrays/3. Challenges/7. Array Chunk.js

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+const chunk = (array, size) => {
+  const chunked = [];
+  let index = 0;
+
+  while (index < array.length) {
+    const chunk = array.slice(index, index + size);
+    // console.log("------------", chunk);
+    chunked.push(chunk);
+    index += size;
+  }
+
+  return chunked;
+};
+
+// console.log(chunk([1, 2, 3, 4, 5], 2));
+console.log(chunk([1, 2, 3, 4, 5, 6, 7, 8], 3));

3. Arrays/3. Challenges/8. Two Sum.js

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+// ⚠️ This is not better solution, we'll make it better in the upcoming videos!
+
+function twoSum(nums, target) {
+  // Loop through each number in the list
+  for (let i = 0; i < nums.length; i++) {
+    // For each number, check the rest of the list
+    for (let j = i + 1; j < nums.length; j++) {
+      // If the current number and the one we're checking add up to the target, return their indexes
+      if (nums[i] + nums[j] === target) {
+        return [i, j];
+      }
+    }
+  }
+
+  // If no matching pair is found, return an empty array
+  return [];
+}
+
+const res = twoSum([2, 7, 11, 15], 9);
+const res2 = twoSum([1, 3, 7, 9, 2], 11);
+console.log(res);
+console.log(res2);