数组中最大的完美平方数

给定一个由n个整数组成的数组。任务是找到最大的数，即一个完美的正方形。如果没有数字是完美的平方，则打印-1。
例子：

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

一个简单的解决方案是对元素进行排序并对n个数字进行排序，然后使用sqrt()函数从后面开始检查一个完美的平方数。从结尾开始的第一个数字是一个完美的平方数是我们的答案。排序的复杂度为O(n log n)，而sqrt()函数的复杂度为log n，因此在最坏的情况下，复杂度为O(n log n)。
一个有效的解决方案是对O(n)中的所有元素进行迭代，并每次与最大元素进行比较，并存储所有完美平方的最大值。
下面是上述方法的实现：

C++

// CPP program to find the largest perfect
// square number among n numbers
 
#include
#include
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;
}

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..

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

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..

Javascript

 
// Javascript 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
    let 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
function largestPerfectSquareNumber(a, n)
{
    // stores the maximum of all
    // perfect square numbers
    let maxi = -1;
 
    // Traverse all elements in the array
    for (let 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
let a = [ 16, 20, 25, 2, 3, 10 ];
let n = a.length;
document.write(largestPerfectSquareNumber(a, n));
 
// This code is contributed by souravmahato348.

输出：

25

时间复杂度： O(n)