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

August LeetCoding Challenge 13

Description

Check if There is a Valid Partition For The Array

You are given a 0-indexed integer array nums. You have to partition the array into one or more contiguous subarrays.

We call a partition of the array valid if each of the obtained subarrays satisfies one of the following conditions:

1. The subarray consists of exactly 2 equal elements. For example, the subarray [2,2] is good.
2. The subarray consists of exactly 3 equal elements. For example, the subarray [4,4,4] is good.
3. The subarray consists of exactly 3 consecutive increasing elements, that is, the difference between adjacent elements is 1. For example, the subarray [3,4,5] is good, but the subarray [1,3,5] is not.

Return true if the array has at least one valid partition. Otherwise, return false.

Example 1:

Input: nums = [4,4,4,5,6]
Output: true
Explanation: The array can be partitioned into the subarrays [4,4] and [4,5,6].
This partition is valid, so we return true.

Example 2:

Input: nums = [1,1,1,2]
Output: false
Explanation: There is no valid partition for this array.

Constraints:

• 2 <= nums.length <= 105
• 1 <= nums[i] <= 106

Solution

auto speedup = [](){
  cin.tie(nullptr);
  cout.tie(nullptr);
  ios::sync_with_stdio(false);
  return 0;
}();
class Solution {
public:
  bool validPartition(vector<int>& nums) {
    int len = nums.size();
    vector<bool> valid(len + 1);
    valid[0] = true;
    if(nums[0] == nums[1]) valid[2] = true;

    for(int i = 3; i <= len; ++i) {
      if(valid[i - 2] && nums[i - 2] == nums[i - 1]) {
        valid[i] = true;
      }
      if(valid[i - 3] && ((nums[i - 3] == nums[i - 2] && nums[i - 3] == nums[i - 1]) ||
                          (nums[i - 3] + 1 == nums[i - 2] && nums[i - 2] + 1 == nums[i - 1]))) {
        valid[i] = true;
      }
    }

    return valid.back();
  }
};

// Accepted
// 117/117 cases passed (65 ms)
// Your runtime beats 100 % of cpp submissions
// Your memory usage beats 92.92 % of cpp submissions (83.9 MB)