Solved @zjming

0946--validate-stack-sequences/Code/1.java

+class Solution {
+    public boolean validateStackSequences(int[] pushed, int[] popped) {
+        
+        int N = pushed.length;
+        Stack<Integer> stack = new Stack();
+        
+        int j = 0;
+        for (int x: pushed) {
+            stack.push(x);
+            while (!stack.isEmpty() && j < N && stack.peek() == popped[j]) {
+                //队头元素出队，栈顶元素出栈
+                stack.pop();
+                j++;
+            }
+        }
+        if (!stack.isEmpty()){
+            return false;
+        }
+        return true;
+    }
+}
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