Largest perfect square number in an Array
Given an array of n integers. The task is to find the largest number which is a perfect square. Print -1 if there is no number that is perfect square.
Examples:
Input : arr[] = {16, 20, 25, 2, 3, 10}
Output : 25
Explanation: 25 is the largest number
that is a perfect square.
Input : arr[] = {36, 64, 10, 16, 29, 25|
Output : 64
A Simple Solution is to sort the elements and sort the n numbers and start checking from back for a perfect square number using sqrt() function. The first number from the end which is a perfect square number is our answer. The complexity of sorting is O(n log n) and of sqrt() function is log n, so at the worst case the complexity is O(n log n).
An Efficient Solution is to iterate for all the elements in O(n) and compare every time with the maximum element, and store the maximum of all perfect squares.
Below is the implementation of the above approach:
C++
// CPP program to find the largest perfect // square number among n numbers #include<iostream> #include<math.h> using namespace std; // Function to check if a number // is perfect square number or not bool checkPerfectSquare(double n) { // takes the sqrt of the number double d = sqrt(n); // checks if it is a perfect // square number if (d * d == n) return true; return false; } // Function to find the largest perfect // square number in the array int largestPerfectSquareNumber(int a[], double n) { // stores the maximum of all // perfect square numbers int maxi = -1; // Traverse all elements in the array for (int i = 0; i < n; i++) { // store the maximum if current // element is a perfect square if (checkPerfectSquare(a[i])) maxi = max(a[i], maxi); } return maxi; } // Driver Code int main() { int a[] = { 16, 20, 25, 2, 3, 10 }; double n = sizeof(a) / sizeof(a[0]); cout << largestPerfectSquareNumber(a, n); return 0; } |
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Java
// Java program to find the largest perfect // square number among n numbers import java.lang.Math; import java.io.*; class GFG { // Function to check if a number // is perfect square number or not static boolean checkPerfectSquare(double n) { // takes the sqrt of the number double d = Math.sqrt(n); // checks if it is a perfect // square number if (d * d == n) return true; return false; } // Function to find the largest perfect // square number in the array static int largestPerfectSquareNumber(int a[], double n) { // stores the maximum of all // perfect square numbers int maxi = -1; // Traverse all elements in the array for (int i = 0; i < n; i++) { // store the maximum if current // element is a perfect square if (checkPerfectSquare(a[i])) maxi = Math.max(a[i], maxi); } return maxi; } // Driver Code public static void main (String[] args) { int []a = { 16, 20, 25, 2, 3, 10 }; double n = a.length; System.out.println( largestPerfectSquareNumber(a, n)); } } // This code is contributed // by inder_verma.. |
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Python3
# Python3 program to find the largest perfect # square number among n numbers # from math lib import sqrt() from math import sqrt # Function to check if a number # is perfect square number or not def checkPerfectSquare(n) : # takes the sqrt of the number d = sqrt(n) # checks if it is a perfect # square number if d * d == n : return True return False # Function to find the largest perfect # square number in the array def largestPerfectSquareNumber(a, n) : # stores the maximum of all # perfect square numbers maxi = -1 # Traverse all elements in the array for i in range(n) : # store the maximum if current # element is a perfect square if(checkPerfectSquare(a[i])) : maxi = max(a[i], maxi) return maxi # Driver code if __name__ == "__main__" : a = [16, 20, 25, 2, 3, 10 ] n = len(a) print(largestPerfectSquareNumber(a, n)) # This code is contributed by Ryuga |
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C#
// C# program to find the largest perfect // square number among n numbers using System; class GFG { // Function to check if a number // is perfect square number or not static bool checkPerfectSquare(double n) { // takes the sqrt of the number double d = Math.Sqrt(n); // checks if it is a perfect // square number if (d * d == n) return true; return false; } // Function to find the largest perfect // square number in the array static int largestPerfectSquareNumber(int []a, double n) { // stores the maximum of all // perfect square numbers int maxi = -1; // Traverse all elements in the array for (int i = 0; i < n; i++) { // store the maximum if current // element is a perfect square if (checkPerfectSquare(a[i])) maxi = Math.Max(a[i], maxi); } return maxi; } // Driver Code public static void Main () { int []a = { 16, 20, 25, 2, 3, 10 }; double n = a.Length; Console.WriteLine( largestPerfectSquareNumber(a, n)); } } // This code is contributed // by inder_verma.. |
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PHP
<?php // PHP program to find the largest perfect // square number among n numbers // Function to check if a number // is perfect square number or not function checkPerfectSquare($n) { // takes the sqrt of the number $d = sqrt($n); // checks if it is a perfect // square number if ($d * $d == $n) return true; return false; } // Function to find the largest perfect // square number in the array function largestPerfectSquareNumber($a, $n) { // stores the maximum of all // perfect square numbers $maxi = -1; // Traverse all elements in the array for ($i = 0; $i <$n; $i++) { // store the maximum if current // element is a perfect square if (checkPerfectSquare($a[$i])) $maxi = max($a[$i], $maxi); } return $maxi; } // Driver Code $a = array( 16, 20, 25, 2, 3, 10 ); $n = count($a); echo largestPerfectSquareNumber($a, $n); // This code is contributed // by inder_verma. ?> |
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Output:
25
Time Complexity : O(n)
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