gold-3-5

栈排序。 编写程序，对栈进行排序使最小元素位于栈顶。最多只能使用一个其他的临时栈存放数据，但不得将元素复制到别的数据结构（如数组）中。该栈支持如下操作：push、pop、peek 和 isEmpty。当栈为空时，peek 返回 -1。

示例1:

 输入：
["SortedStack", "push", "push", "peek", "pop", "peek"]
[[], [1], [2], [], [], []]
 输出：
[null,null,null,1,null,2]

示例2:

 输入： 
["SortedStack", "pop", "pop", "push", "pop", "isEmpty"]
[[], [], [], [1], [], []]
 输出：
[null,null,null,null,null,true]

说明:

1. 栈中的元素数目在[0, 5000]范围内。

//leetcode submit region begin(Prohibit modification and deletion)
class SortedStack {

    private Stack<Integer> myStack;

    public SortedStack() {
        this.myStack = new Stack<>();
    }

    public void push(int val) {
        Stack<Integer> tempStack = new Stack<>();

        while (!this.myStack.isEmpty()) {
            int curValue = this.myStack.pop();
            if (val > curValue) {
                tempStack.push(curValue);
            } else {
                this.myStack.push(curValue);
                this.myStack.push(val);

                while (!tempStack.isEmpty()) {
                    this.myStack.push(tempStack.pop());
                }
                return;
            }
        }

        this.myStack.push(val);

        while (!tempStack.isEmpty()) {
            this.myStack.push(tempStack.pop());
        }
    }

    public void pop() {
        if (!isEmpty()) {
            this.myStack.pop();
        }
    }

    public int peek() {
        if (!isEmpty()) {
            return this.myStack.peek();
        } else {
            return -1;
        }
    }

    public boolean isEmpty() {
        return this.myStack.isEmpty();
    }
}

/**
 * Your SortedStack object will be instantiated and called as such:
 * SortedStack obj = new SortedStack();
 * obj.push(val);
 * obj.pop();
 * int param_3 = obj.peek();
 * boolean param_4 = obj.isEmpty();
 */
//leetcode submit region end(Prohibit modification and deletion)