android-notes/blogs/Algorithm/剑指 Offer/栈相关.md

栈相关

09. 用两个栈实现队列

class CQueue {

    Stack<Integer> putStack, takeStack;

    public CQueue() {
        putStack = new Stack<>();
        takeStack = new Stack<>();
    }

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

    public int deleteHead() {
        if (takeStack.isEmpty()) {
            while (!putStack.isEmpty()) {
                takeStack.push(putStack.pop());
            }
        }
        if (takeStack.isEmpty()) {
            return -1;
        } else {
            return takeStack.pop();
        }
    }
}