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:
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 elements void 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 code int main() { int n = 5, k = 2; int arr[] = {20, 10, 25, 30, 40}; deleteElements(arr, n, k); return 0; } |
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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 |
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Python3
# Function to delete elements def deleteElements(arr, n, k): # create an empty stack st st = [] st.append(arr[0]) # index to mantain 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 code k = 2arr = [20, 10, 25, 30, 40] deleteElements(arr, len(arr), k) # This code is contributed by himan085. |
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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 |
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Output:
25 30 40
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