78 lines
2.3 KiB
Java
78 lines
2.3 KiB
Java
//实现一个MyQueue类，该类用两个栈来实现一个队列。 示例： MyQueue queue = new MyQueue(); queue.push(1);
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//queue.push(2); queue.peek(); // 返回 1 queue.pop(); // 返回 1 queue.empty(); // 返
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//回 false 说明： 你只能使用标准的栈操作 -- 也就是只有 push to top, peek/pop from top, size 和 is empty
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// 操作是合法的。 你所使用的语言也许不支持栈。你可以使用 list 或者 deque（双端队列）来模拟一个栈，只要是标准的栈操作即可。 假设所有操作都是有效的
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//（例如，一个空的队列不会调用 pop 或者 peek 操作）。 Related Topics 栈
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// 👍 35 👎 0
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package leetcode.editor.cn;
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import java.util.Stack;
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//面试题 03.04:化栈为队
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public class ImplementQueueUsingStacksLcci {
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public static void main(String[] args) {
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//测试代码
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// Solution solution = new ImplementQueueUsingStacksLcci().new Solution();
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}
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//力扣代码
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//leetcode submit region begin(Prohibit modification and deletion)
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class MyQueue {
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Stack<Integer> stack1;
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Stack<Integer> stack2;
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/**
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* Initialize your data structure here.
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*/
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public MyQueue() {
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stack1 = new Stack<>();
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stack2 = new Stack<>();
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}
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/**
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* Push element x to the back of queue.
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*/
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public void push(int x) {
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while (!stack1.empty()) {
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stack2.push(stack1.pop());
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}
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stack1.push(x);
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while (!stack2.isEmpty()) {
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stack1.push(stack2.pop());
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}
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}
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/**
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* Removes the element from in front of queue and returns that element.
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*/
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public int pop() {
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return stack1.pop();
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}
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/**
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* Get the front element.
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*/
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public int peek() {
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return stack1.peek();
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}
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/**
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* Returns whether the queue is empty.
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*/
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public boolean empty() {
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return stack1.empty();
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}
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}
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/**
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* Your MyQueue object will be instantiated and called as such:
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* MyQueue obj = new MyQueue();
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* obj.push(x);
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* int param_2 = obj.pop();
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* int param_3 = obj.peek();
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* boolean param_4 = obj.empty();
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*/
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//leetcode submit region end(Prohibit modification and deletion)
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} |