public boolean validateStackSequences(int[] pushed, int[] popped) {
Stack<Integer> stack = new Stack<Integer>();
int j = 0, n = pushed.length, m = popped.length;
for (int i = 0; i < n; ++i) {
stack.add(pushed[i]);
while (!stack.isEmpty() && j < m && stack.peek().equals(popped[j])) {
stack.pop();
j++;
}
}
return stack.isEmpty();
}