LC2919

class Solution {
public:
    long long minIncrementOperations(vector<int>& ns, int k) {
        using ll = long long;
        int n = ns.size();
        vector<ll> dp(n, LLONG_MAX / 2);
        for (int i = 0; i < 3; ++i) dp[i] = (ns[i] >= k ? 0 : k - ns[i]);
        for (int i = 0; i < n; ++i) {
            for (int j = 1; j <= 3 && i + j < n; ++j) {
                ll costj = (ns[i + j] >= k ? 0 : k - ns[i + j]);
                dp[i + j] = min(dp[i + j], dp[i] + costj);
            }
        }
        return min({dp[n-1], dp[n-2], dp[n-3]});
    }
};