1 class Queue {
2 public:
3 // Push element x to the back of queue.
4 void push(int x) {
5 while (!nums.empty()) {
6 nums_assist.push(nums.top());
7 nums.pop();
8 }
9 nums.push(x);
10 while (!nums_assist.empty()) {
11 nums.push(nums_assist.top());
12 nums_assist.pop();
13 }
14 }
15
16 // Removes the element from in front of queue.
17 void pop(void) {
18 nums.pop();
19 }
20
21 // Get the front element.
22 int peek(void) {
23 return nums.top();
24 }
25
26 // Return whether the queue is empty.
27 bool empty(void) {
28 return nums.empty();
29 }
30 private:
31 stack<int> nums, nums_assist;
32 };
