Given two sequences pushed and popped with distinct values, return true if and only if this could have been the result of a sequence of push and pop operations on an initially empty stack.
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.
Time: O(N)
class Solution { public boolean validateStackSequences(int[] pushed, int[] popped) { LinkedList<Integer> stack = new LinkedList<>(); int index = 0; for (int num : pushed) { stack.offerFirst(num); while (!stack.isEmpty() && stack.peekFirst() == popped[index]) { stack.pollFirst(); index += 1; } } return stack.isEmpty(); } }
[LC] 946. Validate Stack Sequences
原文：https://www.cnblogs.com/xuanlu/p/13062883.html