Create Maximum Rectangular Area.java

Author: py3-coder

Stack_Interview Problem/Maximum Rectangular Area.java

@@ -0,0 +1,67 @@
+//Problem Link ::https://practice.geeksforgeeks.org/problems/maximum-rectangular-area-in-a-histogram-1587115620/1?utm_source=gfg&utm_medium=article&utm_campaign=bottom_sticky_on_article
+class Solution
+{
+    //Function to find largest rectangular area possible in a given histogram.
+    public static long getMaxArea(long arr[], long n) 
+    {
+        // your code here
+        //Lets Play with Stack::::
+        int[] right=nsr(arr);
+        int[] left =nsl(arr);
+        
+        //NSR , NSL ::
+       
+        long width=0;
+        long maxi=0;
+        for(int i=0;i<arr.length;i++){
+            width =right[i]-left[i]-1;
+            maxi =Math.max(width*arr[i],maxi);
+        }
+        return maxi;
+    }
+    public static int[] nsr(long[] arr){
+        Stack<Integer> st = new Stack();
+        int[] right=new int[arr.length];
+         for(int i=arr.length-1;i>=0;i--){
+            if(st.isEmpty()){
+                right[i] =arr.length;
+            }else if(arr[st.peek()]<arr[i]){
+                right[i] =st.peek();
+            }else{
+                while(!st.isEmpty() && arr[st.peek()]>=arr[i]){
+                    st.pop();
+                }
+                if(st.isEmpty()){
+                    right[i] =arr.length;
+                }else{
+                    right[i] =st.peek();
+                }
+            }
+            st.push(i);
+        }
+        return right;
+    }
+    public static int[] nsl(long[] arr){
+        int[] left = new int[arr.length];
+        Stack<Integer> st = new Stack();
+        for(int i=0;i<arr.length;i++){
+            if(st.isEmpty()){
+                left[i] =-1;
+            }else if(arr[st.peek()]<arr[i]){
+                left[i] =st.peek();
+            }else{
+                while(!st.isEmpty() && arr[st.peek()]>=arr[i]){
+                    st.pop();
+                }
+                if(st.isEmpty()){
+                    left[i] =-1;
+                }else{
+                    left[i] =st.peek();
+                }
+            }
+            st.push(i);
+        }
+        return left;
+    }
+        
+}