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

November LeetCoding Challenge 19

Description

Reduction Operations to Make the Array Elements Equal

Given an integer array nums, your goal is to make all elements in nums equal. To complete one operation, follow these steps:

1. Find the largest value in nums. Let its index be i (0-indexed) and its value be largest. If there are multiple elements with the largest value, pick the smallest i.
2. Find the next largest value in nums strictly smaller than largest. Let its value be nextLargest.
3. Reduce nums[i] to nextLargest.

Return the number of operations to make all elements in nums equal.

Example 1:

Input: nums = [5,1,3]
Output: 3
Explanation: It takes 3 operations to make all elements in nums equal:
1. largest = 5 at index 0. nextLargest = 3. Reduce nums[0] to 3. nums = [3,1,3].
2. largest = 3 at index 0. nextLargest = 1. Reduce nums[0] to 1. nums = [1,1,3].
3. largest = 3 at index 2. nextLargest = 1. Reduce nums[2] to 1. nums = [1,1,1].

Example 2:

Input: nums = [1,1,1]
Output: 0
Explanation: All elements in nums are already equal.

Example 3:

Input: nums = [1,1,2,2,3]
Output: 4
Explanation: It takes 4 operations to make all elements in nums equal:
1. largest = 3 at index 4. nextLargest = 2. Reduce nums[4] to 2. nums = [1,1,2,2,2].
2. largest = 2 at index 2. nextLargest = 1. Reduce nums[2] to 1. nums = [1,1,1,2,2].
3. largest = 2 at index 3. nextLargest = 1. Reduce nums[3] to 1. nums = [1,1,1,1,2].
4. largest = 2 at index 4. nextLargest = 1. Reduce nums[4] to 1. nums = [1,1,1,1,1].

Constraints:

• 1 <= nums.length <= 5 * 104
• 1 <= nums[i] <= 5 * 104

Solution

class Solution {
public:
  int reductionOperations(vector<int>& nums) {
    map<int, int> count;
    for(auto n : nums) {
      count[n] += 1;
    }
    int answer = 0;
    int prevCount = 0;
    while(count.size() != 1) {
      auto [n, c] = *count.rbegin();
      answer += c + prevCount;
      prevCount += c;
      count.erase(n);
    }
    return answer;
  }
};

// Accepted
// 78/78 cases passed (378 ms)
// Your runtime beats 7.09 % of cpp submissions
// Your memory usage beats 21.23 % of cpp submissions (124.5 MB)