# Validate Stack Sequences

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:

1. `0 <= pushed.length == popped.length <= 1000`
2. `0 <= pushed[i], popped[i] < 1000`
3. `pushed` is a permutation of `popped`.
4. `pushed` and `popped` have distinct values.

## Solution

```public class Solution {
public bool ValidateStackSequences(int[] pushed, int[] popped) {
Stack<int> s = new Stack<int>();

int j = 0;
foreach(int num in pushed){
s.Push(num);

while(s.Count > 0 &&
j < pushed.Length &&
s.Peek() == popped[j]){
s.Pop();
j++;
}
}

return j == popped.Length;
}
}
```

Time Complexity: O(n)

Space Complexity: O(n)

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