Find closest greater value for every element in array
Given an array of integers, find the closest greater element for every element. If there is no greater element then print -1
Examples:
Input : arr[] = {10, 5, 11, 6, 20, 12}
Output : 11 6 12 10 -1 20Input : arr[] = {10, 5, 11, 10, 20, 12}
Output :z 11 10 12 11 -1 20
A simple solution is to run two nested loops. We pick an outer element one by one. For every picked element, we traverse remaining array and find closest greater element. The time complexity of this solution is O(n*n)
A better solution is to use sorting. We sort all elements, then for every element, traverse toward right until we find a greater element (Note that there can be multiple occurrences of an element).
An efficient solution is to use Self Balancing BST (Implemented as set in C++ and TreeSet in Java). In a Self Balancing BST, we can do both insert and closest greater operations in O(Log n) time
Implementation:
C++
// C++ program to find closest greater value // for every array element #include <bits/stdc++.h> using namespace std; void closetGreater( int arr[], int n) { // Insert all array elements into a Set set< int > ts; for ( int i = 0; i < n; i++) ts.insert(arr[i]); // Find smallest greater element for // every array element for ( int i = 0; i < n; i++) { auto greater = ts.upper_bound(arr[i]); if (greater == ts.end()) cout << -1 << " " ; else cout << *greater << " " ; } } // Driver code int main( int argc, char const *argv[]) { int arr[] = {10, 5, 11, 10, 20, 12}; int n = sizeof (arr) / sizeof (arr[0]); closetGreater(arr, n); return 0; } // This code is contributed by // sanjeev2552 |
Java
// Java program to find closest greater value for // every array element import java.util.*; class TreeSetDemo { public static void closestGreater( int [] arr) { // Insert all array elements into a TreeSet TreeSet<Integer> ts = new TreeSet<Integer>(); for ( int i = 0 ; i < arr.length; i++) ts.add(arr[i]); // Find smallest greater element for every // array element for ( int i = 0 ; i < arr.length; i++) { Integer greater = ts.higher(arr[i]); if (greater == null ) System.out.print(- 1 + " " ); else System.out.print(greater + " " ); } } public static void main(String[] args) { int [] arr = { 10 , 5 , 11 , 10 , 20 , 12 }; closestGreater(arr); } } |
Python3
# Python program to find closest greater value # for every array element def upper_bound(s, val): temp = list (s).copy() temp.sort() try : index_value = temp.index(val) if (index_value = = len (temp) - 1 ): return 0 return temp[index_value + 1 ] except ValueError: return arr[ 0 ] def closetGreater(arr, n): # Insert all array elements into a Set ts = set () for i in range (n): ts.add(arr[i]) # Find smallest greater element for # every array element for i in range (n): greater = upper_bound(ts, arr[i]) if (greater = = 0 ): print ( - 1 ,end = " " ) else : print (greater,end = " " ) # Driver code arr = [ 10 , 5 , 11 , 10 , 20 , 12 ] n = len (arr) closetGreater(arr, n) # This code is contributed by shinjanpatra |
C#
// C# program to find closest greater value for // every array element using System; using System.Collections.Generic; public class TreeSetDemo { public static void closestGreater( int [] arr) { // Insert all array elements into a TreeSet SortedSet< int > ts = new SortedSet< int >(); for ( int i = 0; i < arr.Length; i++) ts.Add(arr[i]); // Find smallest greater element for every // array element for ( int i = 0; i < arr.Length; i++) { int greater = upper_bound(ts, arr[i]); if (greater == -1) Console.Write(-1 + " " ); else Console.Write(greater + " " ); } } public static int upper_bound(SortedSet< int > s, int val) { List< int > temp = new List< int >(); temp.AddRange(s); temp.Sort(); if (temp.IndexOf(val) + 1 == temp.Count) return -1; else return temp[temp.IndexOf(val) + 1]; } public static void Main(String[] args) { int [] arr = { 10, 5, 11, 10, 20, 12 }; closestGreater(arr); } } // This code is contributed by Rajput-Ji |
Javascript
<script> // JavaScript program to find closest greater value // for every array element function closetGreater(arr, n) { // Insert all array elements into a Set let ts = new Set(); for (let i = 0; i < n; i++) ts.add(arr[i]); // Find smallest greater element for // every array element for (let i = 0; i < n; i++) { let greater = upper_bound(ts, arr[i]); if (!greater) document.write(-1 + " " ); else document.write(greater + " " ); } } function upper_bound(s, val) { let temp = [...s]; temp.sort((a, b) => a - b); return temp[temp.indexOf(val) + 1]; } // Driver code let arr = [10, 5, 11, 10, 20, 12]; let n = arr.length; closetGreater(arr, n); // This code is contributed by _saurabh_jaiswal </script> |
11 10 12 11 -1 20
Time Complexity: O(n Log n)