1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
#include <bits/stdc++.h>
#include <queue>

using pii = std::pair<int, int>;

int main() {
    int n, k;
    std::cin >> n >> k;

    std::vector<int> tab(n);
    std::priority_queue<pii, std::vector<pii>, std::greater<pii>> q;
    long long answer = 0;

    auto maxneigh = [&](int i) -> int {
        return std::max(
            std::max(
                tab[std::clamp(i - 1, 0, n - 1)], 
                tab[std::clamp(i + 1, 0, n - 1)]
            ), 
            tab[i]
        );
    };

    for (int i = 0; i < n; i++) {
        std::cin >> tab[i];
        q.push({maxneigh(i), i});
    }

    while (!q.empty()) {
        auto e = q.top();
        q.pop();

        int i  = e.second;
        int li = std::clamp(i - 1, 0, n - 1);
        int ri = std::clamp(i + 1, 0, n - 1);

        int new_val = std::max(
            maxneigh(i) - k,
            tab[i]
        );

        answer += new_val - tab[i];
        if (new_val > tab[i]) {
            if (li != i) {
                q.push({maxneigh(li), li});      
            }
            if (ri != i) {
                q.push({maxneigh(ri), ri});      
            }
        }

        tab[i] = new_val;
    }

    std::cout << answer << "\n";
}