You are given an array of n integer and an integer K. Find the number of total unordered pairs {i, j} such that absolute value of (ai + aj – K), i.e., |ai + aj – k| is minimal possible, where i != j.
Examples:
Input: arr[] = {0, 4, 6, 2, 4}, K = 7
Output: Minimal Value = 1, Total Pairs = 5
Explanation: Pairs resulting minimal value are : {a1, a3}, {a2, a4}, {a2, a5}, {a3, a4}, {a4, a5}
Input: arr[] = {4, 6, 2, 4} , K = 9
Output: Minimal Value = 1, Total Pairs = 4
Explanation: Pairs resulting minimal value are : {a1, a2}, {a1, a4}, {a2, a3}, {a2, a4}
A simple solution is iterate over all possible pairs and for each pair we will check whether the value of (ai + aj – K) is smaller than our current smallest value of not. So as per result of above condition we have total of three cases :
- abs( ai + aj – K) > smallest : do nothing as this pair will not count in minimal possible value.
- abs(ai + aj – K) = smallest : increment the count of pair resulting minimal possible value.
- abs( ai + aj – K) < smallest : update the smallest value and set count to 1.
Below is the implementation of the above approach:
C++
#include <bits/stdc++.h>
using namespace std;
void pairs(int arr[], int n, int k)
{
int smallest = INT_MAX;
int count = 0;
for (int i = 0; i < n; i++)
for (int j = i + 1; j < n; j++) {
if (abs(arr[i] + arr[j] - k) < smallest) {
smallest = abs(arr[i] + arr[j] - k);
count = 1;
}
else if (abs(arr[i] + arr[j] - k) == smallest)
count++;
}
cout << "Minimal Value = " << smallest << "\n";
cout << "Total Pairs = " << count << "\n";
}
int main()
{
int arr[] = { 3, 5, 7, 5, 1, 9, 9 };
int k = 12;
int n = sizeof(arr) / sizeof(arr[0]);
pairs(arr, n, k);
return 0;
}
|
Java
import java.util.*;
class GFG {
static void pairs(int arr[], int n, int k)
{
int smallest = Integer.MAX_VALUE;
int count = 0;
for (int i = 0; i < n; i++)
for (int j = i + 1; j < n; j++) {
if (Math.abs(arr[i] + arr[j] - k)
< smallest) {
smallest
= Math.abs(arr[i] + arr[j] - k);
count = 1;
}
else if (Math.abs(arr[i] + arr[j] - k)
== smallest)
count++;
}
System.out.println("Minimal Value = " + smallest);
System.out.println("Total Pairs = " + count);
}
public static void main(String[] args)
{
int arr[] = { 3, 5, 7, 5, 1, 9, 9 };
int k = 12;
int n = arr.length;
pairs(arr, n, k);
}
}
|
Python3
def pairs(arr, n, k):
smallest = 999999999999
count = 0
for i in range(n):
for j in range(i + 1, n):
if abs(arr[i] + arr[j] - k) < smallest:
smallest = abs(arr[i] + arr[j] - k)
count = 1
elif abs(arr[i] + arr[j] - k) == smallest:
count += 1
print("Minimal Value = ", smallest)
print("Total Pairs = ", count)
if __name__ == '__main__':
arr = [3, 5, 7, 5, 1, 9, 9]
k = 12
n = len(arr)
pairs(arr, n, k)
|
C#
using System;
class GFG {
static void pairs(int[] arr, int n, int k)
{
int smallest = 0;
int count = 0;
for (int i = 0; i < n; i++)
for (int j = i + 1; j < n; j++) {
if (Math.Abs(arr[i] + arr[j] - k)
< smallest) {
smallest
= Math.Abs(arr[i] + arr[j] - k);
count = 1;
}
else if (Math.Abs(arr[i] + arr[j] - k)
== smallest)
count++;
}
Console.WriteLine("Minimal Value = " + smallest);
Console.WriteLine("Total Pairs = " + count);
}
public static void Main()
{
int[] arr = { 3, 5, 7, 5, 1, 9, 9 };
int k = 12;
int n = arr.Length;
pairs(arr, n, k);
}
}
|
PHP
<?php
function pairs($arr, $n, $k)
{
$smallest = PHP_INT_MAX;
$count = 0;
for ($i = 0; $i < $n; $i++)
for($j = $i + 1; $j < $n; $j++)
{
if ( abs($arr[$i] + $arr[$j] - $k) < $smallest )
{
$smallest = abs($arr[$i] + $arr[$j] - $k);
$count = 1;
}
else if (abs($arr[$i] +
$arr[$j] - $k) == $smallest)
$count++;
}
echo "Minimal Value = " , $smallest , "\n";
echo "Total Pairs = ", $count , "\n";
}
$arr = array (3, 5, 7, 5, 1, 9, 9);
$k = 12;
$n = sizeof($arr);
pairs($arr, $n, $k);
?>
|
Javascript
<script>
function pairs(arr, n, k)
{
var smallest = 1000000000;
var count=0;
for (var i=0; i<n; i++)
for(var j=i+1; j<n; j++)
{
if ( Math.abs(arr[i] + arr[j] - k) < smallest )
{
smallest = Math.abs(arr[i] + arr[j] - k);
count = 1;
}
else if (Math.abs(arr[i] + arr[j] - k) == smallest)
count++;
}
document.write( "Minimal Value = " + smallest + "<br>");
document.write( "Total Pairs = " + count + "<br>");
}
var arr = [3, 5, 7, 5, 1, 9, 9];
var k = 12;
var n = arr.length;
pairs(arr, n, k);
</script>
|
OutputMinimal Value = 0
Total Pairs = 4
Time Complexity: O(n2) where n is the number of elements in the array.
Auxiliary Space : O(1)
An efficient solution is to use a self balancing binary search tree (which is implemented in set in C++ and TreeSet in Java). We can find closest element in O(log n) time in map.
C++
#include <bits/stdc++.h>
using namespace std;
void pairs(int arr[], int n, int k)
{
int smallest = INT_MAX, count = 0;
set<int> s;
s.insert(arr[0]);
for (int i = 1; i < n; i++) {
int lower
= *lower_bound(s.begin(), s.end(), k - arr[i]);
int upper
= *upper_bound(s.begin(), s.end(), k - arr[i]);
int curr_min = min(abs(lower + arr[i] - k),
abs(upper + arr[i] - k));
if (curr_min < smallest) {
smallest = curr_min;
count = 1;
}
else if (curr_min == smallest)
count++;
s.insert(arr[i]);
}
cout << "Minimal Value = " << smallest << "\n";
cout << "Total Pairs = " << count << "\n";
}
int main()
{
int arr[] = { 3, 5, 7, 5, 1, 9, 9 };
int k = 12;
int n = sizeof(arr) / sizeof(arr[0]);
pairs(arr, n, k);
return 0;
}
|
Python3
from sys import maxsize
from bisect import bisect_left, bisect_right
def pairs(arr, n, k):
smallest = maxsize
count = 0
s = set()
s.add(arr[0])
for i in range(1, n):
sorted_s = sorted(s)
index = bisect_left(sorted_s, k - arr[i])
if index == len(sorted_s):
lower = sorted_s[index - 1]
else:
lower = sorted_s[index]
index = bisect_right(sorted_s, k - arr[i])
if index == len(sorted_s):
upper = sorted_s[index - 1]
else:
upper = sorted_s[index]
curr_min = min(abs(lower + arr[i] - k), abs(upper + arr[i] - k))
if curr_min < smallest:
smallest = curr_min
count = 1
elif curr_min == smallest:
count += 1
s.add(arr[i])
print("Minimal Value = ", smallest)
print("Total Pairs = ", count)
arr = [3, 5, 7, 5, 1, 9, 9]
k = 12
n = len(arr)
pairs(arr, n, k)
|
Java
import java.util.*;
class Main {
static void pairs(final int[] arr,final int n,final int k) {
int smallest = Integer.MAX_VALUE, count = 0;
Set<Integer> s = new TreeSet<>();
s.add(arr[0]);
for (int i = 1; i < n; i++) {
int lower = Integer.MIN_VALUE;
int upper = Integer.MAX_VALUE;
for (Integer x : s) {
if (x <= (k - arr[i]) && x >= lower) {
lower = x;
}
if (x >= (k - arr[i]) && x <= upper) {
upper = x;
}
}
int curr_min = Math.min(Math.abs(lower + arr[i] - k), Math.abs(upper + arr[i] - k));
if (curr_min < smallest) {
smallest = curr_min;
count = 1;
}
else if (curr_min == smallest)
count++;
s.add(arr[i]);
}
System.out.println("Minimal Value = " + smallest);
System.out.println("Total Pairs = " + count);
}
public static void main(String[] args) {
int[] arr = {3, 5, 7, 5, 1, 9, 9};
int k = 12;
int n = arr.length;
pairs(arr, n, k);
}
}
|
Javascript
function pairs(arr, n, k) {
let smallest = Number.MAX_SAFE_INTEGER;
let count = 0;
let s = new Set();
s.add(arr[0]);
for (let i = 1; i < n; i++) {
let lower = [...s].find((element) => element >= k - arr[i]);
let upper = [...s].find((element) => element >= k - arr[i]);
let curr_min = Math.min(Math.abs(lower + arr[i] - k), Math.abs(upper + arr[i] - k));
if (curr_min < smallest) {
smallest = curr_min;
count = 1;
}
else if (curr_min === smallest)
count++;
s.add(arr[i]);
}
console.log(`Minimal Value = ${smallest}`);
console.log(`Total Pairs = ${count}`);
}
let arr = [3, 5, 7, 5, 1, 9, 9];
let k = 12;
let n = arr.length;
pairs(arr, n, k);
|
C#
using System;
using System.Collections.Generic;
using System.Linq;
class Program
{
static void pairs(int[] arr, int n, int k)
{
int smallest = int.MaxValue, count = 0;
SortedSet<int> s = new SortedSet<int>();
s.Add(arr[0]);
for (int i = 1; i < n; i++)
{
int lower = s.Where(e => e >= k - arr[i]).DefaultIfEmpty(int.MinValue).First();
int upper = s.Where(e => e > k - arr[i]).DefaultIfEmpty(int.MaxValue).First();
int curr_min = Math.Min(Math.Abs(lower + arr[i] - k), Math.Abs(upper + arr[i] - k));
if (curr_min < smallest)
{
smallest = curr_min;
count = 1;
}
else if (curr_min == smallest)
{
count++;
}
s.Add(arr[i]);
}
Console.WriteLine("Minimal Value = " + smallest);
Console.WriteLine("Total Pairs = " + count);
}
static void Main(string[] args)
{
int[] arr = { 3, 5, 7, 5, 1, 9, 9 };
int k = 12;
int n = arr.Length;
pairs(arr, n, k);
}
}
|
OutputMinimal Value = 0
Total Pairs = 4
Time Complexity : O(n Log n)
Auxiliary Space: O(n)
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