2025-04-27 Daily Challenge

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In: DailyChallenge

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

April LeetCoding Challenge 27

Description

Count Subarrays of Length Three With a Condition

Given an integer array nums, return the number of subarrays of length 3 such that the sum of the first and third numbers equals exactly half of the second number.

 

Example 1:

Input: nums = [1,2,1,4,1]

Output: 1

Explanation:

Only the subarray [1,4,1] contains exactly 3 elements where the sum of the first and third numbers equals half the middle number.

Example 2:

Input: nums = [1,1,1]

Output: 0

Explanation:

[1,1,1] is the only subarray of length 3. However, its first and third numbers do not add to half the middle number.

 

Constraints:

  • 3 <= nums.length <= 100
  • -100 <= nums[i] <= 100

Solution

class Solution {
public:
  int countSubarrays(vector<int>& nums) {
    int answer = 0;
    for(int i = 0; i + 2 < nums.size(); ++i) {
      answer += ((nums[i] + nums[i + 2]) * 2 == nums[i + 1]);
    }
    return answer;
  }
};

// Accepted
// 1691/1691 cases passed (0 ms)
// Your runtime beats 100 % of cpp submissions
// Your memory usage beats 75.3 % of cpp submissions (48.4 MB)
Algorithm