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Leetcode 232. Implement Queue using Stacks (Easy) (cpp)
Tag: Stack, Design
Difficulty: Easy
/*
232. Implement Queue using Stacks (Easy)
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> s1, s2;
// Push element x to the back of queue.
void push(int x) {
while (!s2.empty()) {
s1.push(s2.top());
s2.pop();
}
s1.push(x);
while (!s1.empty()) {
s2.push(s1.top());
s1.pop();
}
}
// Removes the element from in front of queue.
void pop(void) {
s2.pop();
}
// Get the front element.
int peek(void) {
return s2.top();
}
// Return whether the queue is empty.
bool empty(void) {
return s2.empty();
}
};
本文标签: implementLeetCodeQueuecppEasy
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