剑指offer-31

题目

结果

代码

class Solution {
    public boolean validateStackSequences(int[] pushed, int[] popped) {
        // Stack simulation
        Deque<Integer> stack = new LinkedList<>();
        // Check out if the num has been used
        boolean[] flag = new boolean[pushed.length];

        for (int pop : popped) {
            for (int i = 0; i < pushed.length; i++) {
                // If the num has not been used
                if (!flag[i]) {
                    stack.push(pushed[i]);
                    flag[i] = true;
                }

                if (!stack.isEmpty() && stack.peek() == pop) {
                    stack.pop();
                    break;
                }
            }
        }
        return stack.isEmpty();
    }
}