LeetCode 1827. Minimum Operations to Make the Array Increasing

You are given an integer array nums (0-indexed). In one operation, you can choose an element of the array and increment it by 1.

• For example, if nums = [1,2,3], you can choose to increment nums[1] to make nums = [1,3,3].

Return the minimum number of operations needed to make nums strictly increasing.

An array nums is strictly increasing if nums[i] < nums[i+1] for all 0 <= i < nums.length - 1. An array of length 1 is trivially strictly increasing.

Example 1:

Input: nums = [1,1,1]
Output: 3
Explanation: You can do the following operations:
1) Increment nums[2], so nums becomes [1,1,2].
2) Increment nums[1], so nums becomes [1,2,2].
3) Increment nums[2], so nums becomes [1,2,3].

Example 2:

Input: nums = [1,5,2,4,1]
Output: 14

Example 3:

Input: nums = [8]
Output: 0

Constraints:

• 1 <= nums.length <= 5000

• 1 <= nums[i] <= 104

Solution

class Solution {
public:
    int minOperations(vector<int>& nums) {
        int ans = 0;
        for (int i = 1; i < nums.size(); i++) {
            int previous = nums[i-1];
            int current = nums[i];
            
            if (current <= previous) {
                current = previous + 1;
                ans += (current - nums[i]);
                nums[i] = current;
            }
        }
        
        return ans;
    }
};