Medium946 challenge

Author: konstantin

src/medium/946. Validate Stack Sequences .kt

@@ -0,0 +1,49 @@
+package medium
+
+import ArraysTopic
+import StackTopic
+import java.util.*
+
+/**
+ * 946. Validate Stack Sequences
+ * https://leetcode.com/problems/validate-stack-sequences/
+ *
+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.
+ */
+
+class Medium946 : ArraysTopic, StackTopic {
+
+    fun validateStackSequences(pushed: IntArray, popped: IntArray): Boolean {
+        val stack = Stack<Int>()
+        var i = 0
+        var j = 0
+        while (i < pushed.size || j < popped.size) {
+            if (stack.isEmpty()) {
+                if (i < pushed.size) {
+                    stack.push(pushed[i])
+                    i++
+                } else return false
+            } else {
+                if (j < popped.size) {
+                    if (popped[j] == stack.peek()) {
+                        stack.pop()
+                        j++
+                    } else {
+                        if (i < pushed.size) {
+                            stack.push(pushed[i])
+                            i++
+                        } else return false
+                    }
+                } else return false
+            }
+        }
+        return true
+    }
+}
+
+fun main() {
+    println(Medium946().validateStackSequences(intArrayOf(1, 2, 3, 4, 5), intArrayOf(4, 5, 3, 2, 1)))
+    println(Medium946().validateStackSequences(intArrayOf(1, 2, 3, 4, 5), intArrayOf(4, 3, 5, 1, 2)))
+
+}