adding qforms

Author: mamenesia

qforms/directions.md

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+# --- Directions
+
+Implement a Queue datastructure using two stacks.
+*Do not* create an array inside of the 'Queue' class.
+Queue should implement the methods 'add', 'remove', and 'peek'.
+For a reminder on what each method does, look back
+at the Queue exercise.
+
+# --- Examples
+    const q = new Queue();
+    q.add(1);
+    q.add(2);
+    q.peek();  should returns 1
+    q.remove(); should returns 1
+    q.remove(); should returns 2
+
+
+# --- Solutions
+

qforms/qforms.js

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+// --- Directions
+// Implement a Queue datastructure using two stacks.
+// *Do not* create an array inside of the 'Queue' class.
+// Queue should implement the methods 'add', 'remove', and 'peek'.
+// For a reminder on what each method does, look back
+// at the Queue exercise.
+
+// --- Examples
+//     const q = new Queue();
+//     q.add(1);
+//     q.add(2);
+//     q.peek();  should returns 1
+//     q.remove(); should returns 1
+//     q.remove(); should returns 2
+
+
+// Solution
+
+const Stack = require('./stack');
+
+class Queue {
+  constructor() {
+    this.first = new Stack();
+    this.second = new Stack();
+  }
+
+  add(record) {
+    this.first.push(record);
+  }
+
+  remove() {
+    while(this.first.peek()) {
+      this.second.push(this.first.pop());
+    }
+
+    const record = this.second.pop();
+    
+    while(this.second.peek()) {
+      this.first.push(this.second.pop());
+    }
+
+    return record;
+  }
+
+
+  peek() {
+    while(this.first.peek()) {
+      this.second.push(this.first.pop());
+    }
+
+    const record = this.second.peek();
+
+    while(this.second.peek()) {
+      this.first.push(this.second.pop());
+    }
+  }
+}

qforms/stack.js

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+class Stack {
+  constructor(){
+    this.data = [];
+  }
+
+  add(record) {
+    this.data.push(record);
+  }
+
+  remove() {
+    return this.data.pop();
+  }
+
+  peek(){
+    return this.data[this.data.length -1];
+  }
+}