Arithmetic-triplets.js

/*
You are given a 0-indexed, strictly increasing integer array nums and a positive integer diff. A triplet (i, j, k) is an arithmetic triplet if the following conditions are met:

    i < j < k,
    nums[j] - nums[i] == diff, and
    nums[k] - nums[j] == diff.

Return the number of unique arithmetic triplets.

 

Example 1:

Input: nums = [0,1,4,6,7,10], diff = 3
Output: 2
Explanation:
(1, 2, 4) is an arithmetic triplet because both 7 - 4 == 3 and 4 - 1 == 3.
(2, 4, 5) is an arithmetic triplet because both 10 - 7 == 3 and 7 - 4 == 3. 

Example 2:

Input: nums = [4,5,6,7,8,9], diff = 2
Output: 2
Explanation:
(0, 2, 4) is an arithmetic triplet because both 8 - 6 == 2 and 6 - 4 == 2.
(1, 3, 5) is an arithmetic triplet because both 9 - 7 == 2 and 7 - 5 == 2.

*/

var arithmeticTriplets = function(nums, diff) {
    let hash = new Map();
    let count = 0;

    for(let i = 0; i < nums.length; i++) {
        let temp = nums[ i ] - diff;

        if(hash.has(temp) && hash.has(temp - diff)) {
            count++;
        }
        hash.set(nums[ i ]);

    }

    return count;

};

/*
[0  , 1  ,4  ,6  ,7  ,10]
[-3 ,-2  ,1  ,3  ,4  ,7] - diff
[-6 ,-5 ,-2  ,0  ,1  ,4] - diff*2

all the numers which are common in all 3 sets 

*/