946. Validate Stack Sequences

class Solution {
    public boolean validateStackSequences(int[] pushed, int[] popped) {
        int index = 0;
        Stack<Integer> stack = new Stack<>();
        for (int num : pushed) {
            stack.push(num);

            while (!stack.isEmpty() && popped[index] == stack.peek()) {
                stack.pop();
                index++;
            }
        }

        return stack.isEmpty();
    }
}

Reference

946. Validate Stack Sequences
剑指 Offer 31. 栈的压入、弹出序列