Stack & Queue Complete Course

Author: HuXn-WebDev

5. Stack & Queue/1. Stack/index.js

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+class Node {
+  constructor(value) {
+    this.value = value;
+    this.next = null;
+  }
+}
+
+class Stack {
+  constructor(value) {
+    const newNode = new Node(value);
+    this.first = newNode;
+    this.length = 1;
+  }
+
+  push(value) {
+    const newNode = new Node(value);
+
+    if (this.length === 0) {
+      this.first = newNode;
+    } else {
+      newNode.next = this.first;
+      this.first = newNode;
+      this.length++;
+      return this;
+    }
+  }
+
+  pop() {
+    if (this.length === 0) {
+      return undefined;
+    }
+
+    let temp = this.first;
+    this.first = this.first.next;
+    temp.next = null;
+    this.length--;
+    return temp;
+  }
+
+  top() {
+    if (this.length === 0) {
+      return undefined;
+    }
+    return this.first;
+  }
+}
+
+let theStack = new Stack(0);
+theStack.push(1);
+theStack.push(2);
+// theStack.pop();
+console.log(theStack);

5. Stack & Queue/2. Queue/index.js

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+class Node {
+  constructor(value) {
+    this.value = value;
+    this.next = null;
+  }
+}
+
+class Queue {
+  constructor(value) {
+    const newNode = new Node(value);
+    this.first = newNode;
+    this.last = newNode;
+    this.length = 1;
+  }
+
+  enqueue(value) {
+    const newNode = new Node(value);
+    if (this.length === 0) {
+      this.first = newNode;
+      this.last = newNode;
+    }
+
+    this.last.next = newNode;
+    this.last = newNode;
+    this.length++;
+    return this;
+  }
+
+  dequeue() {
+    if (this.length === 0) {
+      return undefined;
+    }
+
+    let temp = this.first;
+
+    if (this.length === 1) {
+      this.first = null;
+      this.last = null;
+    }
+
+    this.first = this.first.next;
+    temp.next = null;
+    this.length--;
+    return temp;
+  }
+}
+
+let myQueue = new Queue(0);
+myQueue.enqueue(1);
+myQueue.enqueue(2);
+myQueue.dequeue();
+console.log(myQueue);

5. Stack & Queue/3. Challenges/1. Min Stack.js

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+class Node {
+  constructor(value) {
+    this.value = value;
+    this.next = null;
+  }
+}
+
+class Stack {
+  constructor(value) {
+    const newNode = new Node(value);
+    this.first = newNode;
+    this.length = 1;
+  }
+
+  push(value) {
+    const newNode = new Node(value);
+
+    if (this.length === 0) {
+      this.first = newNode;
+    } else {
+      newNode.next = this.first;
+      this.first = newNode;
+      this.length++;
+    }
+    return this;
+  }
+
+  pop() {
+    if (this.length === 0) {
+      return undefined;
+    }
+
+    let temp = this.first;
+    this.first = this.first.next;
+    temp.next = null;
+    this.length--;
+    return temp;
+  }
+
+  top() {
+    if (this.length === 0) {
+      return undefined;
+    }
+    return this.first;
+  }
+
+  min() {
+    if (this.length === 0) {
+      return undefined;
+    }
+
+    let current = this.first;
+    let minValue = current.value;
+
+    while (current.next) {
+      current = current.next;
+      if (current.value < minValue) {
+        console.log(current.value, minValue);
+        minValue = current.value;
+      }
+    }
+
+    return minValue;
+  }
+}
+
+let theStack = new Stack();
+theStack.push(1);
+theStack.push(2);
+theStack.push(3);
+console.log(theStack.min());

5. Stack & Queue/3. Challenges/2. Valid Parenthesis.js

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+const isValidParenthesis = (str) => {
+  // Use a stack to store opening brackets
+  const stack = [];
+
+  // Map opening brackets to their closing counterparts
+  const brackets = {
+    "{": "}",
+    "[": "]",
+    "(": ")",
+  };
+
+  // Loop through each character in the string
+  for (let char of str) {
+    // If it's an opening bracket, push it to the stack
+    if (brackets[char]) {
+      stack.push(char);
+    } else {
+      // If it's a closing bracket, check if it matches the top of the stack
+      const top = stack.pop();
+      if (!top || brackets[top] !== char) {
+        return false;
+      }
+    }
+  }
+
+  // After iterating, check if the stack is empty (all brackets were matched)
+  return stack.length === 0;
+};
+
+console.log(isValidParenthesis("(){}[]")); // true
+console.log(isValidParenthesis("([)]")); // false
+console.log(isValidParenthesis("()")); // true
+console.log(isValidParenthesis("(")); // false

5. Stack & Queue/3. Challenges/3. Reverse String Using Stack.js

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+function reverseString(str) {
+  // Create an empty stack
+  const stack = [];
+
+  // Push each character of the string onto the stack
+  for (let char of str) {
+    stack.push(char);
+  }
+
+  // Initialize an empty string to store the reversed string
+  let reversedStr = "";
+
+  // Pop characters from the stack and build the reversed string
+  while (stack.length > 0) {
+    reversedStr += stack.pop();
+  }
+
+  // Return the reversed string
+  return reversedStr;
+}
+
+const originalString = "hello world";
+const reversedString = reverseString(originalString);
+console.log(reversedString); // Output: dlrow olleh