946. Validate Stack Sequences

🟠   🔖  栈 数组 模拟  🔗 LeetCode

题目

Given two integer arrays pushed and popped each with distinct values, return true if this could have been the result of a sequence of push and pop operations on an initially empty stack, orfalse otherwise.

Example 1:

Input: pushed = [1,2,3,4,5], popped = [4,5,3,2,1]

Output: true

Explanation: We might do the following sequence:

push(1), push(2), push(3), push(4),

pop() -> 4,

push(5),

pop() -> 5, pop() -> 3, pop() -> 2, pop() -> 1

Example 2:

Input: pushed = [1,2,3,4,5], popped = [4,3,5,1,2]

Output: false

Explanation: 1 cannot be popped before 2.

Constraints:

• 1 <= pushed.length <= 1000
• 0 <= pushed[i] <= 1000
• All the elements of pushed are unique.
• popped.length == pushed.length
• popped is a permutation of pushed.

题目大意

给定 pushed 和 popped 两个序列，每个序列中的 值都不重复，只有当它们可能是在最初空栈上进行的推入 push 和弹出 pop 操作序列的结果时，返回 true；否则，返回 false 。

解题思路

这道题可以使用模拟栈的方法进行判断，使用一个辅助栈 stack，模拟 push 和 pop 操作，最后通过判断栈是否为空来得到最终的结果。

具体思路如下：

1. 遍历 pushed 数组，模拟入栈操作，并在每次入栈后，判断是否需要执行出栈操作。
2. 如果当前栈顶元素等于 popped 数组中下一个要出栈的元素，则执行出栈操作。
3. 遍历结束后，判断栈是否为空。

代码