剑指 Offer 31. 栈的压入、弹出序列（java & python3）

半会不会的 无语 感谢题解 用辅助栈

java：

class Solution {
    public boolean validateStackSequences(int[] pushed, int[] popped) {
        Stack stack = new Stack<>();
        int i = 0;
        for(int num : pushed){
            stack.push(num);
            while(!stack.isEmpty() && stack.peek() == popped[i]){
                stack.pop();
                i++;
            }
        }
        return stack.isEmpty();
    }
}

python3:

class Solution:
    def validateStackSequences(self, pushed: List[int], popped: List[int]) -> bool:
        stack, i = [], 0
        for num in pushed:
            stack.append(num)
            while stack and stack[-1] == popped[i]:
                stack.pop()
                i += 1
        return not stack