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g0901_1000.s0946_validate_stack_sequences.readme.md Maven / Gradle / Ivy

946\. Validate Stack Sequences

Medium

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, or_ `false` _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`.