思路：设计两个栈，一个栈作为压入栈，另一个作为弹出栈。
压入栈向弹出栈压入数据的时候，必须一次性全部压入
如果弹出栈不为空，绝对不能向弹出栈中压入数据
如果两个栈都为空，则队列就为空
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| import java.util.Stack;
public class TwoStackQueue {
private Stack<Integer> stackPush;
private Stack<Integer> stackPop;
public static void main(String[] args) {
TwoStackQueue twoStackQueue = new TwoStackQueue();
twoStackQueue.add(1);
twoStackQueue.add(2);
twoStackQueue.add(3);
twoStackQueue.add(4);
twoStackQueue.add(5);
System.out.println("--"+twoStackQueue.poll());
System.out.println("--"+twoStackQueue.peek());
System.out.println("--" + twoStackQueue.poll());
twoStackQueue.add(7);
twoStackQueue.add(8);
System.out.println("--" + twoStackQueue.poll());
System.out.println("--" + twoStackQueue.peek());
System.out.println("--" + twoStackQueue.poll());
System.out.println("--" + twoStackQueue.poll());
System.out.println("--" + twoStackQueue.poll());
System.out.println("--" + twoStackQueue.poll());
System.out.println("--" + twoStackQueue.poll());
System.out.println("--" + twoStackQueue.poll());
System.out.println("--" + twoStackQueue.poll());
System.out.println("--" + twoStackQueue.poll());
}
public TwoStackQueue() {
stackPop = new Stack<>();
stackPush = new Stack<>();
}
public void add(int a) {
this.stackPush.push(new Integer(a));
}
public int poll() {
if(this.stackPop.isEmpty() && this.stackPush.isEmpty()) {
throw new RuntimeException("the queue is empty!");
} else if(this.stackPop.isEmpty()) {
while(!this.stackPush.isEmpty()) {
this.stackPop.push(this.stackPush.pop());
}
}
return this.stackPop.pop().intValue();
}
public int peek() {
if (this.stackPop.isEmpty() && this.stackPush.isEmpty()) {
throw new RuntimeException("the queue is empty!");
} else if (this.stackPop.isEmpty()) {
while (!this.stackPush.isEmpty()) {
this.stackPop.push(this.stackPush.pop());
}
}
return this.stackPop.peek().intValue();
}
}
|
