Count Positive - Negative Pairs

Easy

0/40

Average time to solve is 22m

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30 upvotes

Asked in companies

Problem statement

You have been given an array/list(ARR) of positive and negative integers. Print the number of pairs where:

arr[i] = -arr[j] and i != j

Note:

Given array/list can contain duplicate elements and will not contain '0'.

(arr[i],arr[j]) and (arr[j],arr[i]) are considered same.

Detailed explanation ( Input/output format, Notes, Images )

Input format :

The first line of each test case contains an integers 'N' where 'N' denotes the size of array/list(ARR).

The next line contains 'N' space-separated integers representing array elements.

Output format :

Print the total number of positive-negative pairs present in the array/list.

Note:

You are not required to print the output explicitly, it has already been taken care of. Just implement the function.

Constraints :

1 <= N <= 10^5
-10^9 <= arr[i] <= 10^9

Time Limit: 1 sec

Sample Input 1:

9
-1 3 6 2 5 -4 3 2 -4

Sample Output 1:

Explanation For Sample Input 1:

Since there doesn't exist any positive-negative pair, the Output is '0'.

Sample Input 2:

6
-2 8 2 5 -2 -5

Sample Output 2:

Hint 1

Hint 2

Hint 3

Try to explore every possible pair and check for the required condition.

Approaches (3)

Approach 1

Approach 2

Approach 3

Brute Force Approach

Initialize the totalPairs = 0.
Run two loops first from i = 0 to n-1 and second from j = i+1 to n-1 and if arr[i] == -arr[j] then increase the totalPairs by 1.
Return totalPairs.

Time Complexity

O(N^2), where N is the size of the array.

As we are running two nested loops of size N.

Space Complexity

O(1)

As constant extra space, is used.

(100% EXP penalty)

Count Positive - Negative Pairs

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