solved: validate stack sequences

Author: lambiengcode

README.md

@@ -134,4 +134,30 @@ String intToRoman(int num) {
 
   return result.join();
 }
+```
+
+### Validate Stack Sequences
+
+```dart
+bool validateStackSequences(List<int> pushed, List<int> popped) {
+  List<int> current = [];
+  int indexPush = 0;
+  int indexPop = 0;
+
+  while (indexPush < pushed.length - 1 || indexPop < popped.length - 1) {
+    if (current.contains(popped[indexPop])) {
+      if (current.last == popped[indexPop]) {
+        current.removeLast();
+        indexPop++;
+      } else {
+        return false;
+      }
+    } else {
+      current.add(pushed[indexPush]);
+      indexPush++;
+    }
+  }
+
+  return true;
+}
 ```

validate_stack_sequences.dart

@@ -0,0 +1,38 @@
+void main(List<String> args) {
+  List<List<List<int>>> cases = [
+    [
+      [1, 2, 3, 4, 5],
+      [4, 5, 3, 2, 1]
+    ],
+    [
+      [1, 2, 3, 4, 5],
+      [4, 3, 5, 1, 2]
+    ]
+  ];
+
+  for (final testcase in cases) {
+    print(validateStackSequences(testcase.first, testcase.last));
+  }
+}
+
+bool validateStackSequences(List<int> pushed, List<int> popped) {
+  List<int> current = [];
+  int indexPush = 0;
+  int indexPop = 0;
+
+  while (indexPush < pushed.length - 1 || indexPop < popped.length - 1) {
+    if (current.contains(popped[indexPop])) {
+      if (current.last == popped[indexPop]) {
+        current.removeLast();
+        indexPop++;
+      } else {
+        return false;
+      }
+    } else {
+      current.add(pushed[indexPush]);
+      indexPush++;
+    }
+  }
+
+  return true;
+}