剑指offer31-判断出栈数组合不合法

解法：
申请一个额外栈，模拟出栈入栈过程，遍历出栈数组，只有辅助栈栈顶元素等于当前出栈数组值时，才会弹出。

我的代码：

   public boolean validateStackSequences(int[] pushed, int[] popped) {
    if(pushed==null || popped==null) return false;
        if(pushed.length != popped.length) return false;
        return process(pushed, popped);
    }
    public  boolean process(int[] pushed, int[] poped){
        int index1 =0;
        int index2 = 0;
        Stack<Integer> stack = new Stack<>();
        while(index2 < poped.length && index1 < pushed.length){
            if(pushed[index1] != poped[index2]){
                stack.add(pushed[index1]);
                index1 ++;
            }
            else if(pushed[index1] == poped[index2]){
                index2++;
                index1 ++;
                while(!stack.isEmpty() &&stack.peek() == poped[index2]){
                    index2++;
                    stack.pop();
                }
            }
        }
        return stack.isEmpty();
    }