Today I have done leetcode's March LeetCoding Challenge with cpp.

March LeetCoding Challenge 3

Description

Arithmetic Slices

An integer array is called arithmetic if it consists of at least three elements and if the difference between any two consecutive elements is the same.

• For example, [1,3,5,7,9], [7,7,7,7], and [3,-1,-5,-9] are arithmetic sequences.

Given an integer array nums, return the number of arithmetic subarrays of nums.

A subarray is a contiguous subsequence of the array.

Example 1:

Input: nums = [1,2,3,4]
Output: 3
Explanation: We have 3 arithmetic slices in nums: [1, 2, 3], [2, 3, 4] and [1,2,3,4] itself.

Example 2:

Input: nums = [1]
Output: 0

Constraints:

• 1 <= nums.length <= 5000
• -1000 <= nums[i] <= 1000

Solution

class Solution {
public:
  int numberOfArithmeticSlices(vector<int>& nums) {
    int last = nums.front();
    int count = 0;
    int diff = 0;
    int answer = 0;
    for(auto n : nums) {
      if(n - last == diff) {
        count += 1;
      } else {
        answer += max(0, count - 2) * (count - 1) / 2;
        count = 2;
        diff = n - last;
      }
      last = n;
    }
    answer += max(0, count - 2) * (count - 1) / 2;
    return answer;
  }
};

// Accepted
// 15/15 cases passed (3 ms)
// Your runtime beats 66.63 % of cpp submissions
// Your memory usage beats 88.02 % of cpp submissions (7.3 MB)