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By Vishal Basumatary in Hackerrank —

Hackerrank Pairs Solution

Hackerrank Pairs Solution

.MathJax_SVG_Display {text-align: center; margin: 1em 0em; position: relative; display: block!important; text-indent: 0; max-width: none; max-height: none; min-width: 0; min-height: 0; width: 100%} .MathJax_SVG .MJX-monospace {font-family: monospace} .MathJax_SVG .MJX-sans-serif {font-family: sans-serif} .MathJax_SVG {display: inline; font-style: normal; font-weight: normal; line-height: normal; font-size: 100%; font-size-adjust: none; text-indent: 0; text-align: left; text-transform: none; letter-spacing: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0; min-height: 0; border: 0; padding: 0; margin: 0} .MathJax_SVG * {transition: none; -webkit-transition: none; -moz-transition: none; -ms-transition: none; -o-transition: none} .mjx-svg-href {fill: blue; stroke: blue} .MathJax_SVG_LineBox {display: table!important} .MathJax_SVG_LineBox span {display: table-cell!important; width: 10000em!important; min-width: 0; max-width: none; padding: 0; border: 0; margin: 0}

You will be given an array of integers and a target value.  Determine the number of pairs of array elements that have a difference equal to a target value.

For example, given an array of [1, 2, 3, 4] and a target value of 1, we have three values meeting the condition: , , and .

Function Description

Complete the pairs function below.  It must return an integer representing the number of element pairs having the required difference.

pairs has the following parameter(s):

  • k: an integer, the target difference
  • arr: an array of integers

Input Format.MathJax_SVG_Display {text-align: center; margin: 1em 0em; position: relative; display: block!important; text-indent: 0; max-width: none; max-height: none; min-width: 0; min-height: 0; width: 100%} .MathJax_SVG .MJX-monospace {font-family: monospace} .MathJax_SVG .MJX-sans-serif {font-family: sans-serif} .MathJax_SVG {display: inline; font-style: normal; font-weight: normal; line-height: normal; font-size: 100%; font-size-adjust: none; text-indent: 0; text-align: left; text-transform: none; letter-spacing: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0; min-height: 0; border: 0; padding: 0; margin: 0} .MathJax_SVG * {transition: none; -webkit-transition: none; -moz-transition: none; -ms-transition: none; -o-transition: none} .mjx-svg-href {fill: blue; stroke: blue} .MathJax_SVG_LineBox {display: table!important} .MathJax_SVG_LineBox span {display: table-cell!important; width: 10000em!important; min-width: 0; max-width: none; padding: 0; border: 0; margin: 0}

The first line contains two space-separated integers  and , the size of  and the target value.
The second line contains  space-separated integers of the array .

Constraints.MathJax_SVG_Display {text-align: center; margin: 1em 0em; position: relative; display: block!important; text-indent: 0; max-width: none; max-height: none; min-width: 0; min-height: 0; width: 100%} .MathJax_SVG .MJX-monospace {font-family: monospace} .MathJax_SVG .MJX-sans-serif {font-family: sans-serif} .MathJax_SVG {display: inline; font-style: normal; font-weight: normal; line-height: normal; font-size: 100%; font-size-adjust: none; text-indent: 0; text-align: left; text-transform: none; letter-spacing: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0; min-height: 0; border: 0; padding: 0; margin: 0} .MathJax_SVG * {transition: none; -webkit-transition: none; -moz-transition: none; -ms-transition: none; -o-transition: none} .mjx-svg-href {fill: blue; stroke: blue} .MathJax_SVG_LineBox {display: table!important} .MathJax_SVG_LineBox span {display: table-cell!important; width: 10000em!important; min-width: 0; max-width: none; padding: 0; border: 0; margin: 0}

  • each integer  will be unique

Output Format.MathJax_SVG_Display {text-align: center; margin: 1em 0em; position: relative; display: block!important; text-indent: 0; max-width: none; max-height: none; min-width: 0; min-height: 0; width: 100%} .MathJax_SVG .MJX-monospace {font-family: monospace} .MathJax_SVG .MJX-sans-serif {font-family: sans-serif} .MathJax_SVG {display: inline; font-style: normal; font-weight: normal; line-height: normal; font-size: 100%; font-size-adjust: none; text-indent: 0; text-align: left; text-transform: none; letter-spacing: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0; min-height: 0; border: 0; padding: 0; margin: 0} .MathJax_SVG * {transition: none; -webkit-transition: none; -moz-transition: none; -ms-transition: none; -o-transition: none} .mjx-svg-href {fill: blue; stroke: blue} .MathJax_SVG_LineBox {display: table!important} .MathJax_SVG_LineBox span {display: table-cell!important; width: 10000em!important; min-width: 0; max-width: none; padding: 0; border: 0; margin: 0}

An integer representing the number of pairs of integers whose difference is .

Sample Input.MathJax_SVG_Display {text-align: center; margin: 1em 0em; position: relative; display: block!important; text-indent: 0; max-width: none; max-height: none; min-width: 0; min-height: 0; width: 100%} .MathJax_SVG .MJX-monospace {font-family: monospace} .MathJax_SVG .MJX-sans-serif {font-family: sans-serif} .MathJax_SVG {display: inline; font-style: normal; font-weight: normal; line-height: normal; font-size: 100%; font-size-adjust: none; text-indent: 0; text-align: left; text-transform: none; letter-spacing: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0; min-height: 0; border: 0; padding: 0; margin: 0} .MathJax_SVG * {transition: none; -webkit-transition: none; -moz-transition: none; -ms-transition: none; -o-transition: none} .mjx-svg-href {fill: blue; stroke: blue}

5 2  
1 5 3 4 2

Sample Output.MathJax_SVG_Display {text-align: center; margin: 1em 0em; position: relative; display: block!important; text-indent: 0; max-width: none; max-height: none; min-width: 0; min-height: 0; width: 100%} .MathJax_SVG .MJX-monospace {font-family: monospace} .MathJax_SVG .MJX-sans-serif {font-family: sans-serif} .MathJax_SVG {display: inline; font-style: normal; font-weight: normal; line-height: normal; font-size: 100%; font-size-adjust: none; text-indent: 0; text-align: left; text-transform: none; letter-spacing: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0; min-height: 0; border: 0; padding: 0; margin: 0} .MathJax_SVG * {transition: none; -webkit-transition: none; -moz-transition: none; -ms-transition: none; -o-transition: none} .mjx-svg-href {fill: blue; stroke: blue}

3

Explanation.MathJax_SVG_Display {text-align: center; margin: 1em 0em; position: relative; display: block!important; text-indent: 0; max-width: none; max-height: none; min-width: 0; min-height: 0; width: 100%} .MathJax_SVG .MJX-monospace {font-family: monospace} .MathJax_SVG .MJX-sans-serif {font-family: sans-serif} .MathJax_SVG {display: inline; font-style: normal; font-weight: normal; line-height: normal; font-size: 100%; font-size-adjust: none; text-indent: 0; text-align: left; text-transform: none; letter-spacing: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0; min-height: 0; border: 0; padding: 0; margin: 0} .MathJax_SVG * {transition: none; -webkit-transition: none; -moz-transition: none; -ms-transition: none; -o-transition: none} .mjx-svg-href {fill: blue; stroke: blue} .MathJax_SVG_LineBox {display: table!important} .MathJax_SVG_LineBox span {display: table-cell!important; width: 10000em!important; min-width: 0; max-width: none; padding: 0; border: 0; margin: 0}

There are 3 pairs of integers in the set with a difference of 2: [5,3], [4,2] and [3,1] .

Solution in java8

Approach 1.

import java.io.*;
import java.util.*;

public class Solution {

    public static void main(String[] args) {
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
        Scanner in = new Scanner(System.in);
    	int n = in.nextInt();
    	int k = in.nextInt();
    	int[] c = new int[n];
    	for (int i = 0; i < n; i++) {
    		c[i] = in.nextInt();
    	}
    	Arrays.sort(c);
    	int i = c.length - 1;
    	int j = c.length - 1;
    	int count = 0;
    	while (i > 0) {
    		while(c[i] - c[j] < k && j > 0) j--;
    		if (c[i] - c[j] == k) count++;
    		i--;
    	}
    	System.out.println(count);
    	in.close();
    }
}

Approach 2.

import java.io.*;
import java.util.*;

public class Solution {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int k = in.nextInt();
        
        int pairCount = 0;
        Set<Integer> seen = new HashSet<>();
        
        for (int i = 0; i < n; i++) {
            int x = in.nextInt();
            
            if (Integer.MAX_VALUE - k >= x && seen.contains(x + k)) {
                pairCount++;
            }
            if (Integer.MIN_VALUE + k <= x && seen.contains(x - k)) {
                pairCount++;
            }
            
            seen.add(x);
        }
        
        System.out.println(pairCount);
    }
}

Approach 3.

import java.io.*;
import java.util.*;

public class Solution {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int k = in.nextInt();

        int[] numbers = new int[n];
        for(int i=0; i<n; i++) {
            numbers[i] = in.nextInt();
        }

        Arrays.sort(numbers);

        int count = 0;
        for(int i=0; i<n; i++) {
            for(int j=i; j<n; j++) {

                if(numbers[j] - numbers[i] > k) {
                    break;
                }

                if(Math.abs(numbers[i] - numbers[j]) == k) {
                    count++;
                }
            }
        }

        System.out.println(count);

    }
}

Solution in python3

Approach 1.

#!/usr/bin/py
# Head ends here
def pairs(a,k):
    # a is the list of numbers and k is the difference value
    return len(set(a) & set(x + k for x in a))
# Tail starts here

if __name__ == '__main__':
    a = input().strip()
    a = list(map(int, a.split(' ')))
    _a_size=a[0]
    _k=a[1]
    b = input().strip()
    b = list(map(int, b.split(' ')))
    print(pairs(b,_k))

Approach 2.

#!/usr/bin/py
# Head ends here
def pairs(a,k):
    # a is the list of numbers and k is the difference value
    answer = len(set(a) & set(x+k for x in a))
    return answer
# Tail starts here
if __name__ == '__main__':
    a = input().strip()
    a = list(map(int, a.split(' ')))
    _a_size=a[0]
    _k=a[1]
    b = input().strip()
    b = list(map(int, b.split(' ')))
    print(pairs(b,_k))

Approach 3.

#!/usr/bin/py
# Head ends here
def pairs(a, k):
    d = {}
    answer = 0
    for i in a:
        d[i] = i
    for j in a:
        g = j+k
        if g in d:
            answer +=1
    return answer# Tail starts here
if __name__ == '__main__':
    a = input().strip()
    a = list(map(int, a.split(' ')))
    _a_size=a[0]
    _k=a[1]
    b = input().strip()
    b = list(map(int, b.split(' ')))
    print(pairs(b,_k))

Solution in cpp

Approach 1.

#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    int N,k,i,c=0;
	cin>>N>>k;
	vector<int> v(N);
	for (i = 0; i < N; i++)
	{
		cin>>v[i];
	}
	sort(v.begin(),v.end());
	i=0;
	for(int j = 1; j < N; j++)
	{
		if(v[j]-v[i]==k)
		{
			c++;
			i++;
		}
		else if(v[j]-v[i]>k)
		{
			i++;
			j--;
		}
	}

	cout<<c;
	return 0;
}

Approach 2.

#include <iostream>
#include <algorithm>
using namespace std;

int bsrch(int *a, int l, int h, int val)
{
	if(h<l)
		return -1;
	int m = (l+h)/2;
	if(a[m]==val)
		return m;
	if(a[m]>val)
		bsrch(a,l,m-1,val);
	else bsrch(a,m+1,h,val);
}

int main()
{
	int n,k;
	cin>>n>>k;
	int arr[n];
	for(int i=0;i<n;i++)
		cin>>arr[i];
	sort(arr, arr+n);

	int c=0,loc,t;
	for(int i=0;i<n;i++){
		loc = bsrch(arr,i,n-1,arr[i]+k);
		if(loc!=-1){
			c++; loc++;
			while(loc<n && arr[loc]==arr[i]+k){
				c++; loc++;
			}
		}
	}
	cout<<c<<endl;
	return 0;
}

Approach 3.

#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;

int n, k, a[100000];
int ans = 0;
int head = 0;

void input() {
	cin >> n >> k;
	for(int i = 0; i < n; i++)
		cin >> a[i];
}

int findPairs(int x) {
	int p = a[x];
	while(true) {
		if(head >= n)
			return 0;
		if(a[head]-p == k) {
			head++;
			ans++;
			continue;
		}
		if(a[head]-p > k) {
			return 0;
		}
		if(a[head]-p < k) {
			head++;
			continue;
		}
	}
	return 0;
}

void solve() {
	sort(a,a+n);
	for(int i = 0; i < n; i++) {
		findPairs(i);
	}
	cout << ans << endl;
}

int main() {
	input();
	solve();
    return 0;
}

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