面試題09. 用兩個棧實現隊列

題目：

面試題09. 用兩個棧實現隊列

題解：

232. 用棧實現隊列

代碼：

/**
 * 面試題09
 */
import java.util.*;

public class 面試題09 {

    public static class CQueue {

        Stack<Integer> s1; // 輸入棧
        Stack<Integer> s2; // 輸出棧

        public CQueue() {
            s1 = new Stack<>();
            s2 = new Stack<>();
        }

        public void appendTail(int value) {
            s1.push(value);
        }

        public int deleteHead() {
            if (s1.empty() && s2.empty()) {
                return -1;
            }
            if (s2.isEmpty()) {
                while (!s1.isEmpty()) {
                    s2.push(s1.pop());
                }
            }
            return s2.pop();
        }
    }

    public static void main(String[] args) {
        CQueue obj = new CQueue();
        int value = 5;
        obj.appendTail(value);
        int param_2 = obj.deleteHead();
        System.out.println(param_2);
    }
}

參考：

class CQueue {
    LinkedList<Integer> stack1;
	LinkedList<Integer> stack2;

	public CQueue() {
		stack1 = new LinkedList<>();
		stack2 = new LinkedList<>();
	}

	public void appendTail(int value) {
		stack1.add(value);
	}

	public int deleteHead() {
		if (stack2.isEmpty()) {
			if (stack1.isEmpty()) return -1;
			while (!stack1.isEmpty()) {
				stack2.add(stack1.pop());
			}
			return stack2.pop();
		} else return stack2.pop();
	}
}