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

April LeetCoding Challenge 21

Description

Count the Hidden Sequences

You are given a 0-indexed array of n integers differences, which describes the differences between each pair of consecutive integers of a hidden sequence of length (n + 1). More formally, call the hidden sequence hidden, then we have that differences[i] = hidden[i + 1] - hidden[i].

You are further given two integers lower and upper that describe the inclusive range of values [lower, upper] that the hidden sequence can contain.

• For example, given differences = [1, -3, 4], lower = 1, upper = 6, the hidden sequence is a sequence of length 4 whose elements are in between 1 and 6 (inclusive).

  <ul>
  	<li><code>[3, 4, 1, 5]</code> and <code>[4, 5, 2, 6]</code> are possible hidden sequences.</li>
  	<li><code>[5, 6, 3, 7]</code> is not possible since it contains an element greater than <code>6</code>.</li>
  	<li><code>[1, 2, 3, 4]</code> is not possible since the differences are not correct.</li>
  </ul>
  </li>
  

Return the number of possible hidden sequences there are. If there are no possible sequences, return 0.

Example 1:

Input: differences = [1,-3,4], lower = 1, upper = 6
Output: 2
Explanation: The possible hidden sequences are:
- [3, 4, 1, 5]
- [4, 5, 2, 6]
Thus, we return 2.

Example 2:

Input: differences = [3,-4,5,1,-2], lower = -4, upper = 5
Output: 4
Explanation: The possible hidden sequences are:
- [-3, 0, -4, 1, 2, 0]
- [-2, 1, -3, 2, 3, 1]
- [-1, 2, -2, 3, 4, 2]
- [0, 3, -1, 4, 5, 3]
Thus, we return 4.

Example 3:

Input: differences = [4,-7,2], lower = 3, upper = 6
Output: 0
Explanation: There are no possible hidden sequences. Thus, we return 0.

Constraints:

• n == differences.length
• 1 <= n <= 105
• -105 <= differences[i] <= 105
• -105 <= lower <= upper <= 105

Solution

class Solution {
public:
  int numberOfArrays(vector<int>& differences, int lower, int upper) {
    long long highest = 0;
    long long lowest = 0;
    long long current = 0;
    for(auto diff : differences) {
      current += diff;
      highest = max(highest, current);
      lowest = min(lowest, current);
    }
    return max<long long>(0, (upper - lower) - (highest - lowest) + 1);
  }
};

// Accepted
// 86/86 cases passed (2 ms)
// Your runtime beats 42.19 % of cpp submissions
// Your memory usage beats 16.41 % of cpp submissions (112.7 MB)