Leetcode
2020.04.08 17:55
946. Validate Stack Sequences
조회 수 194 추천 수 0 댓글 0
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.
class Solution { public boolean validateStackSequences(int[] pushed, int[] popped) { int loop = pushed.length; Stack<Integer> stack = new Stack(); int index = 0; //for (int x: pushed) { for(int i=0; i<loop; i++){ //stack.push(x); stack.push(pushed[i]); while (!stack.isEmpty() && index < loop && stack.peek() == popped[index]) { stack.pop(); index++; } } return index == loop; } }
class Solution { public boolean validateStackSequences(int[] pushed, int[] popped) { int loop = pushed.length; int[] stack = new int[loop]; int peek = -1; int curr = 0; for(int i=0; i<loop; i++){ stack[++peek] = pushed[i]; while(peek > -1 && curr < loop && stack[peek] == popped[curr]){ peek--; curr++; } } return curr == loop; } }
[문제] https://leetcode.com/problems/validate-stack-sequences/