计数偶数和奇数乘积的有序对的数量
给定一个 n 个正数的数组，任务是计算具有偶数和奇数乘积的有序对的数量。有序对意味着(a，b)和(b，a)将被认为是不同的。 例:
输入: n = 3，arr[] = {1，2，7} 输出:偶积对= 4，奇积对= 2 有序对是(1，2)，(1，7)，(2，1)，(7，1)，(2，7)，(7，2) 偶积对:(1，7)，(7，1) 偶积对:(1，2)，(2，7)，(2，1)，(7，2) 输入:
方法: 两个数的乘积只有都是奇数时才是奇数。因此:
奇数乘积对的数量=(奇数计数)*(奇数计数–1)
偶数乘积对的数量将是奇数乘积对的数量的倒数。因此:
偶数产品对的数量=对的总数–奇数产品对的数量
以下是上述方法的实现:
C++
// C++ implementation of the above approach
#include <bits/stdc++.h>
using namespace std;
// function to count odd product pair
int count_odd_pair(int n, int a[])
{
int odd = 0, even = 0;
for (int i = 0; i < n; i++) {
// if number is even
if (a[i] % 2 == 0)
even++;
// if number is odd
else
odd++;
}
// count of ordered pairs
int ans = odd * (odd - 1);
return ans;
}
// function to count even product pair
int count_even_pair(int odd_product_pairs, int n)
{
int total_pairs = (n * (n - 1));
int ans = total_pairs - odd_product_pairs;
return ans ;
}
// Driver code
int main()
{
int n = 6;
int a[] = { 2, 4, 5, 9, 1, 8 };
int odd_product_pairs = count_odd_pair(n, a);
int even_product_pairs = count_even_pair(
odd_product_pairs, n);
cout << "Even Product Pairs = "
<< even_product_pairs
<< endl;
cout << "Odd Product Pairs= "
<< odd_product_pairs
<< endl;
return 0;
}
Java 语言(一种计算机语言，尤用于创建网站)
// Java implementation of the above approach
import java.io.*;
class GFG {
// function to count odd product pair
static int count_odd_pair(int n, int a[])
{
int odd = 0, even = 0;
for (int i = 0; i < n; i++) {
// if number is even
if (a[i] % 2 == 0)
even++;
// if number is odd
else
odd++;
}
// count of ordered pairs
int ans = odd * (odd - 1);
return ans;
}
// function to count even product pair
static int count_even_pair(int odd_product_pairs, int n)
{
int total_pairs = (n * (n - 1));
int ans = total_pairs - odd_product_pairs;
return ans;
}
// Driver code
public static void main (String[] args) {
int n = 6;
int []a = { 2, 4, 5, 9, 1, 8 };
int odd_product_pairs = count_odd_pair(n, a);
int even_product_pairs = count_even_pair(
odd_product_pairs, n);
System.out.println( "Even Product Pairs = "+
even_product_pairs );
System.out.println("Odd Product Pairs= "+
odd_product_pairs );
}
}
//This Code is Contributed by ajit
Python 3
# Python3 implementation of
# above approach
# function to count odd product pair
def count_odd_pair(n, a):
odd = 0
even = 0
for i in range(0,n):
# if number is even
if a[i] % 2==0:
even=even+1
# if number is odd
else:
odd=odd+1
# count of ordered pairs
ans = odd * (odd - 1)
return ans
# function to count even product pair
def count_even_pair(odd_product_pairs, n):
total_pairs = (n * (n - 1))
ans = total_pairs - odd_product_pairs
return ans
#Driver code
if __name__=='__main__':
n = 6
a = [2, 4, 5, 9, 1 ,8]
odd_product_pairs = count_odd_pair(n, a)
even_product_pairs = (count_even_pair
(odd_product_pairs, n))
print("Even Product Pairs = "
,even_product_pairs)
print("Odd Product Pairs= "
,odd_product_pairs)
# This code is contributed by
# Shashank_Sharma
C
// C# implementation of the above approach
using System;
public class GFG{
// function to count odd product pair
static int count_odd_pair(int n, int []a)
{
int odd = 0, even = 0;
for (int i = 0; i < n; i++) {
// if number is even
if (a[i] % 2 == 0)
even++;
// if number is odd
else
odd++;
}
// count of ordered pairs
int ans = odd * (odd - 1);
return ans;
}
// function to count even product pair
static int count_even_pair(int odd_product_pairs, int n)
{
int total_pairs = (n * (n - 1));
int ans = total_pairs - odd_product_pairs;
return ans;
}
// Driver code
static public void Main (){
int n = 6;
int []a = { 2, 4, 5, 9, 1, 8 };
int odd_product_pairs = count_odd_pair(n, a);
int even_product_pairs = count_even_pair(
odd_product_pairs, n);
Console.WriteLine( "Even Product Pairs = "+
even_product_pairs );
Console.WriteLine("Odd Product Pairs= "+
odd_product_pairs );
}
}
服务器端编程语言（Professional Hypertext Preprocessor 的缩写）
<?php
// function to count odd product pair
function count_odd_pair($n, $a)
{
$odd = 0 ;
$even = 0 ;
for ($i = 0; $i < $n; $i++)
{
// if number is even
if ($a[$i] % 2 == 0)
$even++;
// if number is odd
else
$odd++;
}
// count of ordered pairs
$ans = $odd * ($odd - 1);
return $ans;
}
// function to count even product pair
function count_even_pair($odd_product_pairs, $n)
{
$total_pairs = ($n * ($n - 1));
$ans = $total_pairs - $odd_product_pairs;
return $ans ;
}
// Driver code
$n = 6;
$a = array( 2, 4, 5, 9, 1, 8 );
$odd_product_pairs = count_odd_pair($n, $a);
$even_product_pairs =
count_even_pair($odd_product_pairs, $n);
echo "Even Product Pairs = ",
$even_product_pairs, "\n";
echo "Odd Product Pairs = ",
$odd_product_pairs, "\n";
// This code is contributed
// by ANKITRAI1
?>
java 描述语言
<script>
// JavaScript implementation of the above approach
// function to count odd product pair
function count_odd_pair(n, a)
{
let odd = 0, even = 0;
for (let i = 0; i < n; i++) {
// if number is even
if (a[i] % 2 == 0)
even++;
// if number is odd
else
odd++;
}
// count of ordered pairs
let ans = odd * (odd - 1);
return ans;
}
// function to count even product pair
function count_even_pair(odd_product_pairs, n)
{
let total_pairs = (n * (n - 1));
let ans = total_pairs - odd_product_pairs;
return ans ;
}
// Driver code
let n = 6;
let a = [ 2, 4, 5, 9, 1, 8 ];
let odd_product_pairs = count_odd_pair(n, a);
let even_product_pairs = count_even_pair(
odd_product_pairs, n);
document.write("Even Product Pairs = "
+ even_product_pairs
+ "<br>");
document.write("Odd Product Pairs= "
+ odd_product_pairs
+ "<br>");
// This code is contributed by Surbhi Tyagi.
</script>
Output:
Even Product Pairs = 24
Odd Product Pairs= 6
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