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LeetCode day321–2894

Everyday has one random leetcode quiz. Today’s quiz is 2894. Divisible and Non-divisible Sums Difference

Description:

You are given positive integers n and m.

Define two integers as follows:

• num1: The sum of all integers in the range [1, n] (both inclusive) that are not divisible by m.
• num2: The sum of all integers in the range [1, n] (both inclusive) that are divisible by m.

Return the integer num1 - num2.

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Example 1:

Input: n = 10, m = 3
Output: 19
Explanation: In the given example:
- Integers in the range [1, 10] that are not divisible by 3 are [1,2,4,5,7,8,10], num1 is the sum of those integers = 37.
- Integers in the range [1, 10] that are divisible by 3 are [3,6,9], num2 is the sum of those integers = 18.
We return 37 - 18 = 19 as the answer.

Example 2:

Input: n = 5, m = 6
Output: 15
Explanation: In the given example:
- Integers in the range [1, 5] that are not divisible by 6 are [1,2,3,4,5], num1 is the sum of those integers = 15.
- Integers in the range [1, 5] that are divisible by 6 are [], num2 is the sum of those integers = 0.
We return 15 - 0 = 15 as the answer.

Example 3:

Input: n = 5, m = 1
Output: -15
Explanation: In the given example:
- Integers in the range [1, 5] that are not divisible by 1 are [], num1 is the sum of those integers = 0.
- Integers in the range [1, 5] that are divisible by 1 are [1,2,3,4,5], num2 is the sum of those integers = 15.
We return 0 - 15 = -15 as the answer.

For each number from 1 to n, if it is divisible by m, subtract it from ans; otherwise, add it.

At the end, return ans as answer.

The time complexity is O(n)

/**
 * @param {number} n
 * @param {number} m
 * @return {number}
 */
var differenceOfSums = function (n, m) {
    let ans = 0

    for (let i = 1; i <= n; i++) {
        if (i % m === 0) {
            ans -= i
        } else {
            ans += i
        }
    }

    return ans
};