Added pattern132.java

Author: agni1402

pattern132.class

@@ -0,0 +1,53 @@
+/*
+Given an array of n integers nums, a 132 pattern is a subsequence of three integers nums[i], nums[j] and nums[k] such that i < j < k and nums[i] < nums[k] < nums[j].
+Return true if there is a 132 pattern in nums, otherwise, return false.
+
+Test Case I:
+Input: nums = [1,2,3,4]
+Output: false
+Explanation: There is no 132 pattern in the sequence.
+
+Test Case II:
+Input: nums = [3,1,4,2]
+Output: true
+Explanation: There is a 132 pattern in the sequence: [1, 4, 2].
+ */
+
+import java.util.*;
+
+public class pattern132{
+    private static boolean find132pattern(int[] nums) {
+        int n = nums.length;
+        if (n < 3)
+            return false;
+        Deque<Integer> decreasingStack = new ArrayDeque<>(n);
+        int maxThirdElement = Integer.MIN_VALUE;
+        for (int i = n - 1; i >= 0; i--) {
+            int currentNumber = nums[i];
+            if (currentNumber < maxThirdElement)
+                return true;  
+            while (!decreasingStack.isEmpty() && decreasingStack.peek() < currentNumber) {
+                maxThirdElement = decreasingStack.pop();
+            }
+            decreasingStack.push(currentNumber);
+        }
+        return false;
+    }
+    public static void main(String[] args){
+        Scanner sc = new Scanner(System.in);
+        int n;
+        System.out.println("Enter the size of the array: ");
+        n = sc.nextInt();
+        int[] nums = new int[n];
+        System.out.println("Enter the elements of the array: ");
+        for(int i=0; i<n; i++){
+            nums[i] = sc.nextInt();
+        }
+        boolean result = find132pattern(nums);
+        if(result){
+            System.out.println("The 132 pattern exixts in an Array");
+        }else{
+            System.out.println("The 132 pattern does not exixts in an Array");
+        }
+    }
+}