Create Next Smallest to Right.java

Author: py3-coder

Stack_Interview Problem/Next Smallest to Right.java

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+//Problem Statement :: https://practice.geeksforgeeks.org/problems/help-classmates--141631/1?utm_source=gfg&utm_medium=article&utm_campaign=bottom_sticky_on_article
+
+class Solution {
+	public static int[] help_classmate(int arr[], int n) 
+	{ 
+	    // Your code goes here
+	    //Lets Play with Stack::: why stack ::
+	    // broute force :: 
+	    // for(int i=0;i<n;i++){
+	   //  for(int j=i-1;j>=0;j--){}  --since j is dependent on i -------think of stack:::   
+	    //}
+	    
+	    int[] res = new int[arr.length];
+	    Stack<Integer> st = new Stack<>();
+	    for(int i=n-1;i>=0;i--){
+	        if(st.isEmpty()){
+	            res[i] =-1;
+	        }else if(st.peek()<arr[i]){
+	            res[i] =st.peek();
+	        }else{
+	            while(!st.isEmpty() && st.peek()>=arr[i]){
+	                st.pop();
+	            }
+	            if(st.isEmpty()){
+	                res[i] =-1;
+	            }else{
+	                res[i] =st.peek();
+	            }
+	        }
+	        st.push(arr[i]);
+	    }
+	    return res;
+	} 
+}