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MyQueue.java
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45 lines (37 loc) · 998 Bytes
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package datastructure.stack.leetcode;
import java.util.Stack;
/**
* @author roseduan
* 用栈实现队列
*/
public class MyQueue {
private Stack<Integer> input;
private Stack<Integer> output;
/** Initialize your data structure here. */
public MyQueue() {
this.input = new Stack<>();
this.output = new Stack<>();
}
/** Push element x to the back of queue. */
public void push(int x) {
input.push(x);
}
/** Removes the element from in front of queue and returns that element. */
public int pop() {
peek();
return output.pop();
}
/** Get the front element. */
public int peek() {
if (output.empty()) {
while (!input.empty()) {
output.push(input.pop());
}
}
return output.peek();
}
/** Returns whether the queue is empty. */
public boolean empty() {
return input.empty() && output.empty();
}
}