# Validate Stack Sequences Problem

## Description

LeetCode Problem 946.

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:

``````1
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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:

``````1
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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.

## Sample C++ Code

``````1
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class Solution {
public:
bool validateStackSequences(vector<int> &push, vector<int> &pop) {
stack<int> s;
for (auto i = 0, j = 0; i < push.size(); ++i) {
s.push(push[i]);
while (!s.empty() && s.top() == pop[j]) {
s.pop();
++j;
}
}
return s.empty();
}
};
``````