Data Structure
Networking
RDBMS
Operating System
Java
MS Excel
iOS
HTML
CSS
Android
Python
C Programming
C++
C#
MongoDB
MySQL
Javascript
PHP
Physics
Chemistry
Biology
Mathematics
English
Economics
Psychology
Social Studies
Fashion Studies
Legal Studies
- Selected Reading
- UPSC IAS Exams Notes
- Developer's Best Practices
- Questions and Answers
- Effective Resume Writing
- HR Interview Questions
- Computer Glossary
- Who is Who
Count pairs formed by distinct element sub-arrays in C++
We are given an array arr[] containing integer elements. The goal is to find the count of pairs that can be formed by elements of sub-arrays of arr[] such that each subarray has only distinct elements. If the array is [ 1,2,2,3,3 ] then subarrays with distinct elements only will be [ 1,2 ] and [ 2,3 ]. And pairs will be (1,2) and (2,3) hence count of pairs is 2.
Let us understand with examples
Input − arr[] = {1,2,5,3 }
Output − Count of pairs formed by distinct element sub-arrays are − 6
Explanation − The subarrays with distinct elements are : [ 1,2,5, 3], possible pairs (1,2), (1,3), (1,5), (2,5), (2,3), (5,3)
Total 6 pairs.
Input − arr[] = {1,2,1,2,3}
Output − Count of pairs formed by distinct element sub-arrays are − 5
Explanation − The subarrays with distinct elements are −
[1,2] - pairs: (1,2) [2,1] - pairs: (2,1) [1,2,3] - pairs : (1,2), (2,3), (1,3) Total pairs : 5
The approach used in the below program is as follows
Take an integer array as input.
Function distinct_pairs(int arr[], int size) takes the array and returns the Count pairs formed by distinct element sub-arrays.
Take the initial count as 0. Take variables start=end=0.
Take a vector check(size, false) to mark elements in the window.
Start loop WHILE till start is less than size
Inside the loop, start another loop WHILE till start less than size AND check[arr[star]] = 0 then set count as start - end and set check[arr[start]] as true and also increment the start by 1.
Start Loop WHILE till end less than start AND start is not equal to the size AND check[arr[start]] = true then set check[arr[end]] = false and also increment the end by 1.
Return the count
Print the result.
Example
#include <bits/stdc++.h>
using namespace std;
int distinct_pairs(int arr[], int size){
int count = 0;
int start = 0;
int end = 0;
vector<bool> check(size, false);
while (start < size){
while (start < size && !check[arr[start]]){
count += (start - end);
check[arr[start]] = true;
start++;
}
while (end < start && (start != size && check[arr[start]])){
check[arr[end]] = false;
end++;
}
}
return count;
}
int main(){
int arr[] = {5, 1, 8, 2, 1, 7, 9, 1};
int size = sizeof(arr) / sizeof(arr[0]);
cout<<"Count of pairs formed by distinct element sub-arrays are: "<< distinct_pairs(arr, size);
return 0;
}Output
If we run the above code it will generate the following output −
Count of pairs formed by distinct element sub-arrays are: 17
82 Views
