Validate Stack Sequences

Similar Problems:

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.

Note:

- 0 <= pushed.length
`= popped.length <`

1000 - 0 <= pushed[i], popped[i] < 1000
- pushed is a permutation of popped.
- pushed and popped have distinct values.

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.

- Solution:

// https://code.dennyzhang.com/validate-stack-sequences // Basic Ideas: two pointers + stack // Complexity: Time O(n), Space O(n) func validateStackSequences(pushed []int, popped []int) bool { stack := []int{} j := 0 for _, v := range pushed { stack = append(stack, v) for len(stack) > 0 && stack[len(stack)-1] == popped[j] { stack = stack[0:len(stack)-1] j++ } } return len(stack) == 0 }