@@ -0,0 +1,50 @@
+/**
+* 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 of popped.
+* pushed and popped have distinct values.
+*/
+public class ValidateStackSequences946 {
+public boolean validateStackSequences(int[] pushed, int[] popped) {
+int i = 0;
+int j = 0;
+int len = pushed.length;
+Stack<Integer> st = new Stack<>();
+while (i < len && j < len) {
+while (!st.isEmpty() && j < len && popped[j] == st.peek()) {
+j++;
+st.pop();
+}
+if (j >= len) break;
+while (i < len && pushed[i] != popped[j]) {
+st.push(pushed[i]);
+i++;
+}
+if (i < len && pushed[i] == popped[j]) {
+st.push(pushed[i]);
+i++;
+}
+}
+while (!st.isEmpty() && j < len && popped[j] == st.peek()) {
+j++;
+st.pop();
+}
+return i == len && j == len && st.isEmpty();
+}
+}