Given an array arr[] of size N, the task is to find the maximum index i such that arr[i] is equal to i. If there is no such index in the array arr[] then print -1.
Examples:
Input: arr[ ] = {-10, -5, 0, 3, 7}
Output: 3
Explanation: Only for i=3, arr[3] = 3Input: arr[ ] = {0, 2, 5, 8, 4}
Output: 4
Approach: Follow the steps below to solve this problem:
- Iterate in the range [N-1, 0] using the variable i:
- If the current element is equal to i, then print i and return.
- If there is no such index, then print -1.
Below is the implementation of the above approach:
C++
// C++ implementation of the above approach #include <bits/stdc++.h> using namespace std; // Function to find the maximum index // i such that arr[i] is equal to i void findLargestIndex(int arr[], int n) { // Traversing the array from // backwards for (int i = n - 1; i >= 0; i--) { // If arr[i] is equal to i if (arr[i] == i) { cout << i << endl; return; } } // If there is no such index cout << -1 << endl; } // Driver code int main() { // Given Input int arr[] = { -10, -5, 0, 3, 7 }; int n = sizeof(arr) / sizeof(arr[0]); // Function Call findLargestIndex(arr, n); return 0; } |
Java
// Java implementation of the above approach import java.io.*; class GFG { // Function to find the maximum index // i such that arr[i] is equal to i static void findLargestIndex(int arr[], int n) { // Traversing the array from // backwards for (int i = n - 1; i >= 0; i--) { // If arr[i] is equal to i if (arr[i] == i) { System.out.println(i); return; } } // If there is no such index System.out.println(-1); } // Driver code public static void main(String[] args) { // Given Input int arr[] = { -10, -5, 0, 3, 7 }; int n = arr.length; // Function Call findLargestIndex(arr, n); } } // This code is contributed by Potta Lokesh |
Python
# Python implementation of the above approach # Function to find the maximum index # i such that arr[i] is equal to i def findLargestIndex(arr, n): # Traversing the array from # backwards for i in range (n): # If arr[i] is equal to i if (arr[i] == i) : print( i ) return # If there is no such index print( -1 ) # Driver code # Given Input arr = [-10, -5, 0, 3, 7 ] n = len(arr) # Function Call findLargestIndex(arr, n) # This code is contributed by shivanisinghss2110 |
C#
// C# implementation of the above approach using System; class GFG { // Function to find the maximum index // i such that arr[i] is equal to i static void findLargestIndex(int []arr, int n) { // Traversing the array from // backwards for (int i = n - 1; i >= 0; i--) { // If arr[i] is equal to i if (arr[i] == i) { Console.Write(i); return; } } // If there is no such index Console.Write(-1); } // Driver code public static void Main(String[] args) { // Given Input int []arr = { -10, -5, 0, 3, 7 }; int n = arr.Length; // Function Call findLargestIndex(arr, n); } } // This code is contributed by shivanisinghss2110 |
Javascript
<script> // JavaScript implementation of the above approach // Function to find the maximum index // i such that arr[i] is equal to i function findLargestIndex( arr, n) { // Traversing the array from // backwards for (var i = n - 1; i >= 0; i--) { // If arr[i] is equal to i if (arr[i] == i) { document.write(i); return ; } } // If there is no such index document.write(-1); } // Driver code // Given Input var arr = [ -10, -5, 0, 3, 7 ]; var n = arr.length; // Function Call findLargestIndex(arr, n); // This code is contributed by shivanisinghss2110 </script> |
Output
3
Time Complexity: O(N)
Auxiliary Space: O(1)
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