Submission #696419

#	Time	Username	Problem	Language	Result	Execution time	Memory
696419		jhwest2	Climbers (RMI18_climbers)	C++14	100 / 100	222 ms	431600 KiB

climbers

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef array<int, 3> P;

const int N = 5050;
const ll INF = 1e18 + 10;

int n, a[N], p;
ll dp[2 * N][2 * N];
bool inq[2 * N][2 * N];

int main() {
    cin.tie(0); ios_base::sync_with_stdio(0);
    cin >> n;
    for (int i = 1; i <= n; i++) {
        int x; cin >> x;
        if (p && a[p - 1] == x)
            continue;
        while (p >= 2 && (a[p - 2] < a[p - 1]) == (a[p - 1] < x))
            --p;
        a[p++] = x;
    }
    n = p;

    for (int i = 0; i <= 2 * n - 2; i++)
        for (int j = i; j <= 2 * n - 2; j++)
            dp[i][j] = INF;
    dp[0][2 * n - 2] = 0;

    auto go = [&](int x, int y, int tx, int ty) {
        int p = (x & 1) ? a[y / 2] : a[x / 2];
        int nx = (x & 1) ? (tx ? x + 1 : x - 1) : (tx ? x + 2 : x - 2);
        int ny = (y & 1) ? (ty ? y - 1 : y + 1) : (ty ? y - 2 : y + 2);
        if (nx < 0 || ny < 0 || nx > 2 * n - 2 || ny > 2 * n - 2)
            return P{ -1, -1, 0 };

        bool dx = (tx ? a[nx / 2 - 1] : a[nx / 2 + 1]) < a[nx / 2]; // true if climbing
        bool dy = (ty ? a[ny / 2 + 1] : a[ny / 2 - 1]) < a[ny / 2];

        if (dx != dy)
            return P{ -1, -1, 0 };

        if (a[nx / 2] == a[ny / 2])
            return P{ nx, ny, abs(a[nx / 2] - p) };
        if (dx == (a[nx / 2] < a[ny / 2]))
            return P{ nx, ty ? ny + 1 : ny - 1, abs(a[nx / 2] - p) };
        else
            return P{ tx ? nx - 1 : nx + 1, ny, abs(a[ny / 2] - p) };
    };
    priority_queue<array<ll, 3>> pq;
    pq.push({ 0, 0, 2 * n - 2 });
    
    while (!pq.empty()) {
        auto [d, l, r] = pq.top(); pq.pop();
        d = -d;
        if (l == r)
            break;

        for (int tx = 0; tx <= 1; tx++) for (int ty = 0; ty <= 1; ty++) {
            auto [x, y, d] = go(l, r, tx, ty);
            if (x != -1) {
                if (dp[x][y] > dp[l][r] + d) {
                    dp[x][y] = dp[l][r] + d;
                    pq.push({ -dp[x][y], x, y });
                }
            }
        }
    }
    ll ans = INF;
    for (int i = 0; i < n; i++)
        ans = min(ans, dp[2 * i][2 * i]);
    cout << ans;
}

Compilation message (stderr)

climbers.cpp: In function 'int main()':
climbers.cpp:56:14: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
   56 |         auto [d, l, r] = pq.top(); pq.pop();
      |              ^
climbers.cpp:62:18: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
   62 |             auto [x, y, d] = go(l, r, tx, ty);
      |                  ^

• Subtask 1: 25 / 25
• Subtask 2: 25 / 25
• Subtask 3: 50 / 50