Completed Design-2(Hash Map, Queue Stack)

queuestack.cpp

@@ -0,0 +1,45 @@
+class MyQueue {
+
+    // stack used for pushing new elements
+    stack<int> inSt;
+
+    // stack used for popping and peeking elements
+    stack<int> outSt;
+
+public:
+
+    // constructor initializes empty stacks
+    MyQueue() {}
+
+    // pushes element x to the back of the queue
+    void push(int x) {
+        inSt.push(x);
+    }
+
+    // removes and returns the element from the front of the queue
+    int pop() {
+        // ensure out stack has the front element
+        peek();
+
+        int val = outSt.top();
+        outSt.pop();
+        return val;
+    }
+
+    // returns the element at the front of the queue
+    int peek() {
+        // if out stack is empty, transfer all elements from in stack
+        if (outSt.empty()) {
+            while (!inSt.empty()) {
+                outSt.push(inSt.top());
+                inSt.pop();
+            }
+        }
+        return outSt.top();
+    }
+
+    // returns true if the queue is empty
+    bool empty() {
+        return inSt.empty() && outSt.empty();
+    }
+};