Delete array elements which are smaller than next or become smaller
Given an array arr[] and a number k. The task is to delete k elements which are smaller than next element (i.e., we delete arr[i] if arr[i] < arr[i+1]) or become smaller than next because next element is deleted.
Examples:
Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready. To complete your preparation from learning a language to DS Algo and many more, please refer Complete Interview Preparation Course.
In case you wish to attend live classes with experts, please refer DSA Live Classes for Working Professionals and Competitive Programming Live for Students.
Input : arr[] = { 3, 100, 1 }
k = 1
Output : 100, 1
Explanation : arr[0] < arr[1] means 3 is less than
100, so delete 3
Input : arr[] = {20, 10, 25, 30, 40}
k = 2
Output : 25 30 40
Explanation : First we delete 10 because it follows
arr[i] < arr[i+1]. Then we delete 20
because 25 is moved next to it and it
also starts following the condition.
Input : arr[] = { 23, 45, 11, 77, 18}
k = 3
Output : 77, 18
Explanation : We delete 23, 45 and 11 as they follow
the condition arr[i] < arr[i+1]Approach: Stack is used to solving this problem. First we push arr[0] in stack S and then initialize count as 0, then after traverse a loop from 1 to n and then we check that s.top() < arr[i] if condition is true then we pop the element from stack and increase the count if count == k then we stop the loop and then store the value of stack in another array and then print that array.
C++
// C++ program to delete elements from array.#include <bits/stdc++.h>using namespace std;// Function for deleting k elementsvoid deleteElements(int arr[], int n, int k){ // Create a stack and push arr[0] stack<int> s; s.push(arr[0]); int count = 0; // traversing a loop from i = 1 to n for (int i=1; i<n; i++) { // condition for deleting an element while (!s.empty() && s.top() < arr[i] && count < k) { s.pop(); count++; } s.push(arr[i]); } // Putting elements of stack in a vector // from end to begin. int m = s.size(); vector<int> v(m); // Size of vector is m while (!s.empty()) { // push element from stack to vector v v[--m] = s.top(); s.pop(); } // printing result for (auto x : v) cout << x << " "; cout << endl;}// Driver codeint main(){ int n = 5, k = 2; int arr[] = {20, 10, 25, 30, 40}; deleteElements(arr, n, k); return 0;} |
Java
import java.util.*;//Java program to delete elements from array.class GFG {// Function for deleting k elements static void deleteElements(int arr[], int n, int k) { // Create a stack and push arr[0] Stack<Integer> s = new Stack<>(); s.push(arr[0]); int count = 0; // traversing a loop from i = 1 to n for (int i = 1; i < n; i++) { // condition for deleting an element while (!s.empty() && s.peek() < arr[i] && count < k) { s.pop(); count++; } s.push(arr[i]); } // Putting elements of stack in a vector // from end to begin. int m = s.size(); Integer[] v = new Integer[m]; // Size of vector is m while (!s.empty()) { // push element from stack to vector v v[--m] = s.peek(); s.pop(); } // printing result for (Integer x : v) { System.out.print(x + " "); }; System.out.println(""); }// Driver code public static void main(String[] args) { int n = 5, k = 2; int arr[] = {20, 10, 25, 30, 40}; deleteElements(arr, n, k); }}// This code is contributed by PrinciRaj1992 |
Python3
# Function to delete elementsdef deleteElements(arr, n, k): # create an empty stack st st = [] st.append(arr[0]) # index to maintain the top # of the stack top = 0 count = 0 for i in range(1, n): # pop till the present element # is greater than stack's top # element while(len(st) != 0 and count < k and st[top] < arr[i]): st.pop() count += 1 top -= 1 st.append(arr[i]) top += 1 # print the remaining elements for i in range(0, len(st)): print(st[i], " ", end="")# Driver codek = 2arr = [20, 10, 25, 30, 40]deleteElements(arr, len(arr), k)# This code is contributed by himan085. |
C#
// C# program to delete elements from array.using System;using System.Collections.Generic;class GFG { // Function for deleting k elements static void deleteElements(int []arr, int n, int k) { // Create a stack and push arr[0] Stack<int> s = new Stack<int>(); s.Push(arr[0]); int count = 0; // traversing a loop from i = 1 to n for (int i = 1; i < n; i++) { // condition for deleting an element while (s.Count != 0 && s.Peek() < arr[i] && count < k) { s.Pop(); count++; } s.Push(arr[i]); } // Putting elements of stack in a vector // from end to begin. int m = s.Count; int[] v = new int[m]; // Size of vector is m while (s.Count != 0) { // push element from stack to vector v v[--m] = s.Peek(); s.Pop(); } // printing result foreach (int x in v) { Console.Write(x + " "); }; Console.Write(""); } // Driver code public static void Main() { int n = 5, k = 2; int []arr = {20, 10, 25, 30, 40}; deleteElements(arr, n, k); }}// This code is contributed by 29AjayKumar |
Javascript
<script>// Javascript program to delete elements from array.// Function for deleting k elementsfunction deleteElements(arr, n, k){ // Create a stack and push arr[0] var s = []; s.push(arr[0]); var count = 0; // Traversing a loop from i = 1 to n for(var i = 1; i < n; i++) { // condition for deleting an element while (s.length != 0 && s[s.length - 1] < arr[i] && count < k) { s.pop(); count++; } s.push(arr[i]); } // Putting elements of stack in a vector // from end to begin. var m = s.length; var v = Array(m).fill(0); // Size of vector is m while (s.length != 0) { // push element from stack to vector v m--; v[m] = s[s.length - 1]; s.pop(); } // printing result v.forEach(x => { document.write(x + " "); });}// Driver codevar n = 5, k = 2;var arr = [ 20, 10, 25, 30, 40 ]deleteElements(arr, n, k);// This code is contributed by itsok</script> |
Output:
25 30 40
