给定一个由N 个整数组成的数组arr[] ,任务是计算有效对(i, j) 的数量,使得arr[i] + arr[j] = arr[i] / arr[j] 。
例子:
Input: arr[] = {-4, -3, 0, 2, 1}
Output: 1
Explanation: The only possible pair is (0, 3) which satisfies the condition ( -4 + 2 = -4 / 2 (= -2) ).
Input: arr[] = {1, 2, 3, 4, 5}
Output: 0
朴素的方法:简单的方法是生成给定数组的所有可能对,并计算总和等于它们的除法的对的数量。检查后,所有对打印可能对的最终计数。
下面是上述方法的实现:
C++14
// C++ program for the above approach
#include
using namespace std;
// Function to count all pairs (i, j)
// such that a[i] + [j] = a[i] / a[j]
int countPairs(int a[], int n)
{
// Stores total count of pairs
int count = 0;
// Generate all possible pairs
for (int i = 0; i < n; i++) {
for (int j = i + 1; j < n; j++) {
if (a[j] != 0
&& a[i] % a[j] == 0) {
// If a valid pair is found
if ((a[i] + a[j])
== (a[i] / a[j]))
// Increment count
count++;
}
}
}
// Return the final count
return count;
}
// Driver Code
int main()
{
int arr[] = { -4, -3, 0, 2, 1 };
int N = sizeof(arr) / sizeof(arr[0]);
cout << countPairs(arr, N);
return 0;
}
Java
// Java program for the above approach
import java.util.*;
class GFG
{
// Function to count all pairs (i, j)
// such that a[i] + [j] = a[i] / a[j]
static int countPairs(int a[], int n)
{
// Stores total count of pairs
int count = 0;
// Generate all possible pairs
for (int i = 0; i < n; i++)
{
for (int j = i + 1; j < n; j++)
{
if (a[j] != 0
&& a[i] % a[j] == 0) {
// If a valid pair is found
if ((a[i] + a[j])
== (a[i] / a[j]))
// Increment count
count++;
}
}
}
// Return the final count
return count;
}
// Driver Code
public static void main(String[] args)
{
int arr[] = { -4, -3, 0, 2, 1 };
int N = arr.length;
System.out.print(countPairs(arr, N));
}
}
// This code is contributed by code_hunt.
Python3
# Python3 program for the above approach
# Function to count all pairs (i, j)
# such that a[i] + [j] = a[i] / a[j]
def countPairs(a, n):
# Stores total count of pairs
count = 0
# Generate all possible pairs
for i in range(n):
for j in range(i + 1, n):
if (a[j] != 0 and a[i] % a[j] == 0):
# If a valid pair is found
if ((a[i] + a[j]) == (a[i] // a[j])):
# Increment count
count += 1
# Return the final count
return count
# Driver Code
if __name__ == '__main__':
arr =[-4, -3, 0, 2, 1]
N = len(arr)
print (countPairs(arr, N))
# This code is contributed by mohit kumar 29.
C#
// C# program for the above approach
using System;
class GFG {
// Function to count all pairs (i, j)
// such that a[i] + [j] = a[i] / a[j]
static int countPairs(int[] a, int n)
{
// Stores total count of pairs
int count = 0;
// Generate all possible pairs
for (int i = 0; i < n; i++)
{
for (int j = i + 1; j < n; j++)
{
if (a[j] != 0
&& a[i] % a[j] == 0)
{
// If a valid pair is found
if ((a[i] + a[j])
== (a[i] / a[j]))
// Increment count
count++;
}
}
}
// Return the final count
return count;
}
// Driver code
static void Main() {
int[] arr = { -4, -3, 0, 2, 1 };
int N = arr.Length;
Console.WriteLine(countPairs(arr, N));
}
}
// This code is contributed by divyeshrabadiya07.
Javascript
C++
// C++ program for the above approach
#include
using namespace std;
// Function to find number of pairs
// with equal sum and quotient
// from a given array
int countPairs(int a[], int n)
{
// Store the count of pairs
int count = 0;
// Stores frequencies
map mp;
// Traverse the array
for (int i = 0; i < n; i++) {
int y = a[i];
// If y is neither 1 or 0
if (y != 0 && y != 1) {
// Evaluate x
double x = ((y * 1.0)
/ (1 - y))
* y;
// Increment count by frequency
// of x
count += mp[x];
}
// Update map
mp[y]++;
}
// Print the final count
return count;
}
// Driver Code
int main()
{
int arr[] = { -4, -3, 0, 2, 1 };
int N = sizeof(arr) / sizeof(arr[0]);
// Function Call
cout << countPairs(arr, N);
return 0;
}
Java
// Java program for the above approach
import java.util.*;
class GFG
{
// Function to find number of pairs
// with equal sum and quotient
// from a given array
static int countPairs(int a[], int n)
{
// Store the count of pairs
int count = 0;
// Stores frequencies
HashMap mp = new HashMap();
// Traverse the array
for (int i = 0; i < n; i++)
{
double y = a[i];
// If y is neither 1 or 0
if (y != 0 && y != 1)
{
// Evaluate x
double x = ((y * 1.0)
/ (1 - y))
* y;
// Increment count by frequency
// of x
if(mp.containsKey(x))
count += mp.get(x);
}
// Update map
if(mp.containsKey(y)){
mp.put(y, mp.get(y)+1);
}
else{
mp.put(y, 1);
}
}
// Print the final count
return count;
}
// Driver Code
public static void main(String[] args)
{
int arr[] = { -4, -3, 0, 2, 1 };
int N = arr.length;
// Function Call
System.out.print(countPairs(arr, N));
}
}
// This code is contributed by 29AjayKumar
Python3
# Python3 program for the above approach
# Function to find number of pairs
# with equal sum and quotient
# from a given array
def countPairs(a, n) :
# Store the count of pairs
count = 0
# Stores frequencies
mp = {}
# Traverse the array
for i in range(n):
y = a[i]
# If y is neither 1 or 0
if (y != 0 and y != 1) :
# Evaluate x
x = (((y * 1.0)
// (1 - y))
* y)
# Increment count by frequency
# of x
count += mp.get(x, 0)
# Update map
mp[y] = mp.get(y, 0) + 1
# Prthe final count
return count
# Driver Code
arr = [ -4, -3, 0, 2, 1 ]
N = len(arr)
# Function Call
print(countPairs(arr, N))
# This code is contributed by susmitakundugoaldanga.
C#
// C# program for the above approach
using System;
using System.Collections.Generic;
class GFG
{
// Function to find number of pairs
// with equal sum and quotient
// from a given array
static int countPairs(int[] a, int n)
{
// Store the count of pairs
int count = 0;
// Stores frequencies
Dictionary mp
= new Dictionary();
// Traverse the array
for (int i = 0; i < n; i++) {
int y = a[i];
// If y is neither 1 or 0
if (y != 0 && y != 1) {
// Evaluate x
double x = ((y * 1.0) / (1 - y)) * y;
// Increment count by frequency
// of x
if (!mp.ContainsKey(x))
mp[x] = 0;
count += mp[x];
}
// Update map
if (!mp.ContainsKey(y))
mp[y] = 0;
mp[y]++;
}
// Print the final count
return count;
}
// Driver Code
public static void Main()
{
int[] arr = { -4, -3, 0, 2, 1 };
int N = arr.Length;
// Function Call
Console.Write(countPairs(arr, N));
}
}
// This code is contributed by ukasp.
Javascript
1
时间复杂度: O(N 2 )
辅助空间: O(N)
高效方法:可以通过简化给定表达式并使用 Map 计算满足以下简化条件的对数来优化上述方法:
Suppose X and Y are numbers present in indices i and j, then the condition that needs to be satisfied is:
=> X + Y = X/Y
=> X = Y 2/(1 – Y)
请按照以下步骤解决上述问题:
- 初始化一个变量,例如count ,以存储满足所需条件的所有可能对的计数。
- 初始化一个 Map 来存储为每个数组元素获得的上述表达式的值的频率。
- 使用变量i遍历给定数组并执行以下步骤:
- 如果arr[i]不等于1和0 ,则计算arr[i] 2 /(1 – arr[i]) ,比如X 。
- 将X在Map 中的频率添加到count 。
- 在Map中将arr[i]的频率增加1 。
- 完成上述步骤后,打印计数的值作为结果。
下面是上述方法的实现:
C++
// C++ program for the above approach
#include
using namespace std;
// Function to find number of pairs
// with equal sum and quotient
// from a given array
int countPairs(int a[], int n)
{
// Store the count of pairs
int count = 0;
// Stores frequencies
map mp;
// Traverse the array
for (int i = 0; i < n; i++) {
int y = a[i];
// If y is neither 1 or 0
if (y != 0 && y != 1) {
// Evaluate x
double x = ((y * 1.0)
/ (1 - y))
* y;
// Increment count by frequency
// of x
count += mp[x];
}
// Update map
mp[y]++;
}
// Print the final count
return count;
}
// Driver Code
int main()
{
int arr[] = { -4, -3, 0, 2, 1 };
int N = sizeof(arr) / sizeof(arr[0]);
// Function Call
cout << countPairs(arr, N);
return 0;
}
Java
// Java program for the above approach
import java.util.*;
class GFG
{
// Function to find number of pairs
// with equal sum and quotient
// from a given array
static int countPairs(int a[], int n)
{
// Store the count of pairs
int count = 0;
// Stores frequencies
HashMap mp = new HashMap();
// Traverse the array
for (int i = 0; i < n; i++)
{
double y = a[i];
// If y is neither 1 or 0
if (y != 0 && y != 1)
{
// Evaluate x
double x = ((y * 1.0)
/ (1 - y))
* y;
// Increment count by frequency
// of x
if(mp.containsKey(x))
count += mp.get(x);
}
// Update map
if(mp.containsKey(y)){
mp.put(y, mp.get(y)+1);
}
else{
mp.put(y, 1);
}
}
// Print the final count
return count;
}
// Driver Code
public static void main(String[] args)
{
int arr[] = { -4, -3, 0, 2, 1 };
int N = arr.length;
// Function Call
System.out.print(countPairs(arr, N));
}
}
// This code is contributed by 29AjayKumar
蟒蛇3
# Python3 program for the above approach
# Function to find number of pairs
# with equal sum and quotient
# from a given array
def countPairs(a, n) :
# Store the count of pairs
count = 0
# Stores frequencies
mp = {}
# Traverse the array
for i in range(n):
y = a[i]
# If y is neither 1 or 0
if (y != 0 and y != 1) :
# Evaluate x
x = (((y * 1.0)
// (1 - y))
* y)
# Increment count by frequency
# of x
count += mp.get(x, 0)
# Update map
mp[y] = mp.get(y, 0) + 1
# Prthe final count
return count
# Driver Code
arr = [ -4, -3, 0, 2, 1 ]
N = len(arr)
# Function Call
print(countPairs(arr, N))
# This code is contributed by susmitakundugoaldanga.
C#
// C# program for the above approach
using System;
using System.Collections.Generic;
class GFG
{
// Function to find number of pairs
// with equal sum and quotient
// from a given array
static int countPairs(int[] a, int n)
{
// Store the count of pairs
int count = 0;
// Stores frequencies
Dictionary mp
= new Dictionary();
// Traverse the array
for (int i = 0; i < n; i++) {
int y = a[i];
// If y is neither 1 or 0
if (y != 0 && y != 1) {
// Evaluate x
double x = ((y * 1.0) / (1 - y)) * y;
// Increment count by frequency
// of x
if (!mp.ContainsKey(x))
mp[x] = 0;
count += mp[x];
}
// Update map
if (!mp.ContainsKey(y))
mp[y] = 0;
mp[y]++;
}
// Print the final count
return count;
}
// Driver Code
public static void Main()
{
int[] arr = { -4, -3, 0, 2, 1 };
int N = arr.Length;
// Function Call
Console.Write(countPairs(arr, N));
}
}
// This code is contributed by ukasp.
Javascript
1
时间复杂度: O(N*log N)
辅助空间: O(N)
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