1+ package medium
2+ 3+ import ArraysTopic
4+ import StackTopic
5+ import java.util.*
6+ 7+ /* *
8+ * 946. Validate Stack Sequences
9+ * https://leetcode.com/problems/validate-stack-sequences/
10+ *
11+ Given two integer arrays pushed and popped each with distinct values,
12+ 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.
13+ */
14+ 15+ class Medium946 : ArraysTopic , StackTopic {
16+ 17+ fun validateStackSequences (pushed : IntArray , popped : IntArray ): Boolean {
18+ val stack = Stack <Int >()
19+ var i = 0
20+ var j = 0
21+ while (i < pushed.size || j < popped.size) {
22+ if (stack.isEmpty()) {
23+ if (i < pushed.size) {
24+ stack.push(pushed[i])
25+ i++
26+ } else return false
27+ } else {
28+ if (j < popped.size) {
29+ if (popped[j] == stack.peek()) {
30+ stack.pop()
31+ j++
32+ } else {
33+ if (i < pushed.size) {
34+ stack.push(pushed[i])
35+ i++
36+ } else return false
37+ }
38+ } else return false
39+ }
40+ }
41+ return true
42+ }
43+ }
44+ 45+ fun main () {
46+ println (Medium946 ().validateStackSequences(intArrayOf(1 , 2 , 3 , 4 , 5 ), intArrayOf(4 , 5 , 3 , 2 , 1 )))
47+ println (Medium946 ().validateStackSequences(intArrayOf(1 , 2 , 3 , 4 , 5 ), intArrayOf(4 , 3 , 5 , 1 , 2 )))
48+ 49+ }
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