Welcome to Subscribe On Youtube
Formatted question description: https://leetcode.ca/all/946.html
946. Validate Stack Sequences (Medium)
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 ofpopped
.pushed
andpopped
have distinct values.
Related Topics:
Stack
Solution 1.
-
class Solution { public boolean validateStackSequences(int[] pushed, int[] popped) { Stack<Integer> stack = new Stack<Integer>(); int length = pushed.length; int pushIndex = 0, popIndex = 0; while (pushIndex < length && popIndex < length) { stack.push(pushed[pushIndex]); pushIndex++; while (!stack.isEmpty() && stack.peek() == popped[popIndex]) { stack.pop(); popIndex++; } } return stack.isEmpty(); } } ############ class Solution { public boolean validateStackSequences(int[] pushed, int[] popped) { Deque<Integer> stk = new ArrayDeque<>(); int j = 0; for (int v : pushed) { stk.push(v); while (!stk.isEmpty() && stk.peek() == popped[j]) { stk.pop(); ++j; } } return j == pushed.length; } }
-
// OJ: https://leetcode.com/problems/validate-stack-sequences/ // Time: O(N) // Space: O(N) class Solution { public: bool validateStackSequences(vector<int>& pushed, vector<int>& popped) { stack<int> s; int p = 0; for (int i : pushed) { s.push(i); while (s.size() && s.top() == popped[p]) { s.pop(); ++p; } } return s.empty(); } };
-
class Solution: def validateStackSequences(self, pushed: List[int], popped: List[int]) -> bool: j, stk = 0, [] for v in pushed: stk.append(v) while stk and stk[-1] == popped[j]: stk.pop() j += 1 return j == len(pushed) ############ class Solution(object): def validateStackSequences(self, pushed, popped): """ :type pushed: List[int] :type popped: List[int] :rtype: bool """ stack = [] N = len(pushed) pi = 0 for i in range(N): if stack and popped[i] == stack[-1]: stack.pop() else: while pi < N and pushed[pi] != popped[i]: stack.append(pushed[pi]) pi += 1 pi += 1 return not stack
-
func validateStackSequences(pushed []int, popped []int) bool { stk := []int{} j := 0 for _, v := range pushed { stk = append(stk, v) for len(stk) > 0 && stk[len(stk)-1] == popped[j] { stk = stk[:len(stk)-1] j++ } } return j == len(pushed) }
-
function validateStackSequences(pushed: number[], popped: number[]): boolean { const stk = []; let j = 0; for (const v of pushed) { stk.push(v); while (stk.length && stk[stk.length - 1] == popped[j]) { stk.pop(); ++j; } } return j == pushed.length; }
-
/** * @param {number[]} pushed * @param {number[]} popped * @return {boolean} */ var validateStackSequences = function (pushed, popped) { let stk = []; let j = 0; for (const v of pushed) { stk.push(v); while (stk.length && stk[stk.length - 1] == popped[j]) { stk.pop(); ++j; } } return j == pushed.length; };
-
public class Solution { public bool ValidateStackSequences(int[] pushed, int[] popped) { Stack<int> stk = new Stack<int>(); int j = 0; foreach (int x in pushed) { stk.Push(x); while (stk.Count != 0 && stk.Peek() == popped[j]) { stk.Pop(); ++j; } } return stk.Count == 0; } }
-
impl Solution { pub fn validate_stack_sequences(pushed: Vec<i32>, popped: Vec<i32>) -> bool { let mut stack = Vec::new(); let mut i = 0; for &num in pushed.iter() { stack.push(num); while !stack.is_empty() && *stack.last().unwrap() == popped[i] { stack.pop(); i += 1; } } stack.len() == 0 } }