C16 - Cedar - Afina Walton

lib/problems.js

@@ -0,0 +1,55 @@
+function balanced(string) {
+    // implement stack to check balanced strings
+    let matches = {
+        '(': ')',
+        '{': '}',
+        '[': ']',
+    }
+
+    let stack = [];
+    // if open, add to stack
+    for (let char of string) {
+        if (char in matches) {
+            stack.push(char);
+            continue;
+        } else {
+            let popped = stack.pop();
+            if (matches[popped] === char) continue;
+            else return false;
+        }
+    }
+
+    if (stack.length) return false;
+    return true;
+}
+
+function evaluatePostfix(expr) {
+    let operations = {
+        '+': add = (a, b) => a + b,
+        '*': mult = (a, b) => a * b,
+        '-': subtract = (a, b) => a - b,
+        '/': divide = (a, b) => a / b,
+    }
+
+    let stack = [];
+    let newNum = 0;
+
+    for (let char of expr) {
+        if (char in operations) {
+            if (stack.length > 1) {
+                let popA = +stack.shift();
+                let popB = +stack.shift();
+                newNum = Math.floor(operations[char](popA, popB));
+            } else if (stack.length === 1) {
+                let popped = +stack.shift();
+                newNum = Math.floor(operations[char](newNum, popped));
+            }
+        } else {
+            stack.push(char);
+            continue;
+        }
+    }
+    if (stack.length === 0) return newNum;
+}
+
+module.exports = { balanced, evaluatePostfix }

lib/queue.js

@@ -1,27 +1,59 @@
 class Queue {
+    #front;
+    #rear;
+
     constructor() {
-        // this.store = ...
-        throw new Error("This method has not been implemented!");
+        this.store = new Array(20);
+        // front and rear are index refs
+        this.#front = this.#rear = 0;
     }
 
-    enqueue(element) {
-        throw new Error("This method has not been implemented!");
+    enqueue(element) {        
+        if (
+            (this.#front === 0 && this.#rear === this.size() - 1)
+        ) {
+            throw 'QueueFullException'
+        }
+        else if (this.isEmpty()) {
+            this.store[this.#front] = element;
+        } else {
+            this.#rear += 1;
+            this.store[this.#rear] = element;
+        }
+
+        return;
     }
 
     dequeue() {
-        throw new Error("This method has not been implemented!");
+        if (this.isEmpty()) {
+            throw 'QueueEmptyException'
+        }
+
+        const data = this.store[this.#front];
+        this.store[this.#front] = null;
+
+        if (this.#front === this.#rear) {
+            this.#front = this.#rear = -1;
+        } else if (this.#front === this.size() - 1) {
+            this.#front = 0;
+        } else {
+            this.#front += 1
+        }
+
+        return data;
     }
 
     front() {
-        throw new Error("This method has not been implemented!");
+        return this.store[this.#front];
     }
 
     size() {
-        throw new Error("This method has not been implemented!");
+        return this.store.length;
     }
 
     isEmpty() {
-        throw new Error("This method has not been implemented!");
+        if (this.#front === this.#rear && !this.store[this.#front]) return true
+        return false;
     }
 
     toString() {

lib/stack.js

@@ -1,19 +1,24 @@
+const LinkedList = require("./linked-list");
+
 class Stack {
     constructor() {
-        // this.store = ...
-        throw new Error("This method has not been implemented!");
+        this.store = new LinkedList();
     }
 
-    push() {
-        throw new Error("This method has not been implemented!");
+    push(element) {
+        this.store.addLast(element);
+        return;
     }
 
     pop() {
-        throw new Error("This method has not been implemented!");
+        const toRemove = this.store.getLast();
+        this.store.delete(toRemove);
+
+        return toRemove;
     }
 
     isEmpty() {
-        throw new Error("This method has not been implemented!");
+        return this.store.isEmpty();
     }
 
     toString() {

package.json

@@ -10,9 +10,12 @@
   "scripts": {
     "test": "jest"
   },
+  "jest": {
+    "verbose": true
+  },
   "author": "",
   "license": "ISC",
   "dependencies": {
-    "jest": "^26.4.2"
+    "jest": "^27.5.1"
   }
 }