给定一个数组arr [] ,任务是查找数组中已经存在平方的数组元素的数量。
例子:
Input: arr[] = {2, 4, 5, 20, 16}
Output: 2
Explanation:
{2, 4} has their squares {4, 16} present in the array.
Input: arr[] = {1, 30, 3, 8, 64}
Output: 2
Explanation:
{1, 8} has their squares {1, 64} present in the array.
天真的方法:请按照以下步骤解决问题:
- 初始化一个变量,例如count ,以存储所需的计数。
- 遍历数组,并对每个数组元素执行以下操作:
- 遍历数组并搜索数组中是否存在当前元素的平方。
- 如果找到平方,则增加计数。
- 打印计数作为答案。
下面是上述方法的实现:
C++14
// C++ program for the above approach
#include
using namespace std;
// Function to find the count of elements whose
// squares are already present int the array
void countSquares(int arr[], int N)
{
// Stores the required count
int count = 0;
// Traverse the array
for (int i = 0; i < N; i++) {
// Square of the element
int square = arr[i] * arr[i];
// Traverse the array
for (int j = 0; j < N; j++) {
// Check whether the value
// is equal to square
if (arr[j] == square) {
// Increment count
count = count + 1;
}
}
}
// Print the count
cout << count;
}
// Driver Code
int main()
{
// Given array
int arr[] = { 2, 4, 5, 20, 16 };
// Size of the array
int N = sizeof(arr) / sizeof(arr[0]);
countSquares(arr, N);
return 0;
}
Java
// Java program for the above approach
import java.util.*;
class GFG{
// Function to find the count of elements whose
// squares are already present int the array
static void countSquares(int arr[], int N)
{
// Stores the required count
int count = 0;
// Traverse the array
for (int i = 0; i < N; i++)
{
// Square of the element
int square = arr[i] * arr[i];
// Traverse the array
for (int j = 0; j < N; j++)
{
// Check whether the value
// is equal to square
if (arr[j] == square)
{
// Increment count
count = count + 1;
}
}
}
// Print the count
System.out.print(count);
}
// Driver Code
public static void main(String[] args)
{
// Given array
int arr[] = { 2, 4, 5, 20, 16 };
// Size of the array
int N = arr.length;
countSquares(arr, N);
}
}
// This code is contributed by shikhasingrajput
Python3
# Python program for the above approach
# Function to find the count of elements whose
# squares are already present the array
def countSquares(arr, N):
# Stores the required count
count = 0;
# Traverse the array
for i in range(N):
# Square of the element
square = arr[i] * arr[i];
# Traverse the array
for j in range(N):
# Check whether the value
# is equal to square
if (arr[j] == square):
# Increment count
count = count + 1;
# Prthe count
print(count);
# Driver Code
if __name__ == '__main__':
# Given array
arr = [2, 4, 5, 20, 16];
# Size of the array
N = len(arr);
countSquares(arr, N);
# This code is contributed by shikhasingrajput
C#
// C# program of the above approach
using System;
class GFG{
// Function to find the count of elements whose
// squares are already present int the array
static void countSquares(int[] arr, int N)
{
// Stores the required count
int count = 0;
// Traverse the array
for(int i = 0; i < N; i++)
{
// Square of the element
int square = arr[i] * arr[i];
// Traverse the array
for(int j = 0; j < N; j++)
{
// Check whether the value
// is equal to square
if (arr[j] == square)
{
// Increment count
count = count + 1;
}
}
}
// Print the count
Console.WriteLine(count);
}
// Driver code
static void Main()
{
// Given array
int[] arr = { 2, 4, 5, 20, 16 };
// Size of the array
int N = arr.Length;
countSquares(arr, N);
}
}
// This code is contributed by divyeshrabadiya07
Javascript
C++14
// C++ program for the above approach
#include
using namespace std;
// Function to find the count of elements whose
// squares is already present int the array
int countSquares(int arr[], int N)
{
// Stores the count of array elements
int count = 0;
// Stores frequency of visited elements
unordered_map m;
// Traverse the array
for (int i = 0; i < N; i++) {
m[arr[i]] = m[arr[i]] + 1;
}
for (int i = 0; i < N; i++) {
// Square of the element
int square = arr[i] * arr[i];
// Update the count
count += m[square];
}
// Print the count
cout << count;
}
// Driver Code
int main()
{
// Given array
int arr[] = { 2, 4, 5, 20, 16 };
// Size of the array
int N = sizeof(arr) / sizeof(arr[0]);
// Function Call
countSquares(arr, N);
return 0;
}
Java
// Java program for the above approach
import java.util.*;
class GFG
{
// Function to find the count of elements whose
// squares is already present int the array
static void countSquares(int arr[], int N)
{
// Stores the count of array elements
int count = 0;
// Stores frequency of visited elements
HashMap mp = new HashMap();
// Traverse the array
for (int i = 0; i < N; i++)
{
if(mp.containsKey(arr[i]))
{
mp.put(arr[i], mp.get(arr[i]) + 1);
}
else
{
mp.put(arr[i], 1);
}
}
for (int i = 0; i < N; i++)
{
// Square of the element
int square = arr[i] * arr[i];
// Update the count
count += mp.containsKey(square)?mp.get(square):0;
}
// Print the count
System.out.print(count);
}
// Driver Code
public static void main(String[] args)
{
// Given array
int arr[] = { 2, 4, 5, 20, 16 };
// Size of the array
int N = arr.length;
// Function Call
countSquares(arr, N);
}
}
// This code is contributed by 29AjayKumar
Python3
# Python 3 program for the above approach
from collections import defaultdict
# Function to find the count of elements whose
# squares is already present int the array
def countSquares( arr, N):
# Stores the count of array elements
count = 0;
# Stores frequency of visited elements
m = defaultdict(int);
# Traverse the array
for i in range(N):
m[arr[i]] = m[arr[i]] + 1
for i in range( N ):
# Square of the element
square = arr[i] * arr[i]
# Update the count
count += m[square]
# Print the count
print(count)
# Driver Code
if __name__ == "__main__":
# Given array
arr = [ 2, 4, 5, 20, 16 ]
# Size of the array
N = len(arr)
# Function Call
countSquares(arr, N);
# This code is contributed by chitranayal.
C#
# Python 3 program for the above approach
from collections import defaultdict
# Function to find the count of elements whose
# squares is already present int the array
def countSquares(arr, N):
# Stores the count of array elements
count = 0
# Stores frequency of visited elements
m = defaultdict(int)
# Traverse the array
for i in range(N):
m[arr[i]] = m[arr[i]] + 1
for i in range(N):
# Square of the element
square = arr[i] * arr[i]
# Update the count
count += m[square]
# Print the count
print(count)
# Driver Code
if __name__ == "__main__":
# Given array
arr = [2, 4, 5, 20, 16]
# Size of the array
N = len(arr)
# Function Call
countSquares(arr, N)
Javascript
输出:
2
时间复杂度: O(N 2 )
辅助空间: O(1)
高效的方法:最佳方法是使用unordered_map保留访问元素的计数并相应地更新变量计数。步骤如下:
- 初始化Map来存储数组元素的频率,并初始化变量,例如count 。
- 遍历数组,并为每个元素在Map中增加其计数。
- 再次遍历数组,对于每个元素,检查图中元素的平方频率,并将其添加到变量计数中。
- 打印计数为数组中已存在其正方形的元素数。
下面是上述方法的实现:
C++ 14
// C++ program for the above approach
#include
using namespace std;
// Function to find the count of elements whose
// squares is already present int the array
int countSquares(int arr[], int N)
{
// Stores the count of array elements
int count = 0;
// Stores frequency of visited elements
unordered_map m;
// Traverse the array
for (int i = 0; i < N; i++) {
m[arr[i]] = m[arr[i]] + 1;
}
for (int i = 0; i < N; i++) {
// Square of the element
int square = arr[i] * arr[i];
// Update the count
count += m[square];
}
// Print the count
cout << count;
}
// Driver Code
int main()
{
// Given array
int arr[] = { 2, 4, 5, 20, 16 };
// Size of the array
int N = sizeof(arr) / sizeof(arr[0]);
// Function Call
countSquares(arr, N);
return 0;
}
Java
// Java program for the above approach
import java.util.*;
class GFG
{
// Function to find the count of elements whose
// squares is already present int the array
static void countSquares(int arr[], int N)
{
// Stores the count of array elements
int count = 0;
// Stores frequency of visited elements
HashMap mp = new HashMap();
// Traverse the array
for (int i = 0; i < N; i++)
{
if(mp.containsKey(arr[i]))
{
mp.put(arr[i], mp.get(arr[i]) + 1);
}
else
{
mp.put(arr[i], 1);
}
}
for (int i = 0; i < N; i++)
{
// Square of the element
int square = arr[i] * arr[i];
// Update the count
count += mp.containsKey(square)?mp.get(square):0;
}
// Print the count
System.out.print(count);
}
// Driver Code
public static void main(String[] args)
{
// Given array
int arr[] = { 2, 4, 5, 20, 16 };
// Size of the array
int N = arr.length;
// Function Call
countSquares(arr, N);
}
}
// This code is contributed by 29AjayKumar
Python3
# Python 3 program for the above approach
from collections import defaultdict
# Function to find the count of elements whose
# squares is already present int the array
def countSquares( arr, N):
# Stores the count of array elements
count = 0;
# Stores frequency of visited elements
m = defaultdict(int);
# Traverse the array
for i in range(N):
m[arr[i]] = m[arr[i]] + 1
for i in range( N ):
# Square of the element
square = arr[i] * arr[i]
# Update the count
count += m[square]
# Print the count
print(count)
# Driver Code
if __name__ == "__main__":
# Given array
arr = [ 2, 4, 5, 20, 16 ]
# Size of the array
N = len(arr)
# Function Call
countSquares(arr, N);
# This code is contributed by chitranayal.
C#
# Python 3 program for the above approach
from collections import defaultdict
# Function to find the count of elements whose
# squares is already present int the array
def countSquares(arr, N):
# Stores the count of array elements
count = 0
# Stores frequency of visited elements
m = defaultdict(int)
# Traverse the array
for i in range(N):
m[arr[i]] = m[arr[i]] + 1
for i in range(N):
# Square of the element
square = arr[i] * arr[i]
# Update the count
count += m[square]
# Print the count
print(count)
# Driver Code
if __name__ == "__main__":
# Given array
arr = [2, 4, 5, 20, 16]
# Size of the array
N = len(arr)
# Function Call
countSquares(arr, N)
Java脚本
输出:
2
时间复杂度: O(N)
辅助空间: O(N)
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