946. Validate Stack Sequences

T: O(n)
S: O(n)

```java
class Solution {
    public boolean validateStackSequences(int[] pushed, int[] popped) {
        Stack<Integer> stack = new Stack<>();
        int j = 0;

        for (int i = 0; i < pushed.length; i++) {
            stack.push(pushed[i]);
            while (!stack.isEmpty() && stack.peek() == popped[j]) {
                stack.pop();
                j++;
            }
        }
        return stack.isEmpty();
    }
}


/*




T: O(n)
s: O(n)

*/
```