Implement Queue using Stacks
Implement the following operations of a queue using stacks.
push(x) – Push element x to the back of queue.
pop() – Removes the element from in front of queue.
peek() – Get the front element.
empty() – Return whether the queue is empty.
Notes:
You must use only standard operations of a stack – which means only push to top, peek/pop from top, size, and is empty operations are valid.
Depending on your language, stack may not be supported natively. You may simulate a stack by using a list or deque (double-ended queue), as long as you use only standard operations of a stack.
You may assume that all operations are valid (for example, no pop or peek operations will be called on an empty queue).
class Queue {
public:
stack<int>res;
// Push element x to the back of queue.
void push(int x) {
stack<int>test;
while(res.empty()!=true)
{
test.push(res.top());
res.pop();
}
test.push(x);
while(test.empty()!=true)
{
res.push(test.top());
test.pop();
}
}
// Removes the element from in front of queue.
void pop(void) {
res.pop();
}
// Get the front element.
int peek(void) {
return res.top();
}
// Return whether the queue is empty.
bool empty(void) {
return res.empty();
}
};
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