456-java-solution

Author: crazysamurai

java/456-132-Pattern.java

@@ -0,0 +1,23 @@
+class Solution {
+    /*
+     * Mono Stack
+     * TC: O(n)
+     * SC: O(n)
+     */
+    public boolean find132pattern(int[] nums) {
+        int n = nums.length;
+        Stack<Integer> st = new Stack<>();
+        int secondMax = Integer.MIN_VALUE;
+
+        for (int x = n - 1; x >= 0; x--) {
+            if (nums[x] < secondMax)
+                return true;
+
+            while (!st.isEmpty() && st.peek() < nums[x])
+                secondMax = Math.max(st.pop(), secondMax);
+
+            st.push(nums[x]);
+        }
+        return false;
+    }
+}