Submission #1040154

#	Time	Username	Problem	Language	Result	Execution time	Memory
1040154		TAhmed33	Cat Exercise (JOI23_ho_t4)	C++98	21 / 100	17 ms	14888 KiB

Main

#include <bits/stdc++.h>
using namespace std;
const int MAXN = 2e5 + 25;
int a[MAXN], n;
int nxt[MAXN], prv[MAXN];
vector <int> adj[MAXN];
int dfs (int pos, int l, int r) {
    if (adj[pos].empty()) return 0;
    if ((int)adj[pos].size() == 1) {
        if (adj[pos][0] < pos) {
            return dfs(adj[pos][0], l, pos - 1) + pos - adj[pos][0];
        } else {
            return dfs(adj[pos][0], pos + 1, r) + adj[pos][0] - pos;
        }
    } else {
        return max(dfs(adj[pos][0], l, pos - 1) + pos - adj[pos][0], dfs(adj[pos][1], pos + 1, r) + adj[pos][1] - pos);
    }
}
void solve () {
    cin >> n;
    a[0] = 1e9;
    for (int i = 1; i <= n; i++) {
        cin >> a[i];
    }
    stack <int> cur;
    for (int i = 1; i <= n; i++) {
        while (!cur.empty() && a[i] > a[cur.top()]) {
            nxt[cur.top()] = i;
            cur.pop();
        }
        cur.push(i);
    }
    while (!cur.empty()) cur.pop();
    for (int i = n; i >= 1; i--) {
        while (!cur.empty() && a[i] > a[cur.top()]) {
            prv[cur.top()] = i;
            cur.pop();
        }
        cur.push(i);
    }
    while (!cur.empty()) cur.pop();
    for (int i = 1; i <= n; i++) {
        if (a[nxt[i]] < a[prv[i]]) {
            adj[nxt[i]].push_back(i);
        } else {
            adj[prv[i]].push_back(i);
        }
    }
    adj[0].clear();
    int root = -1;
    for (int i = 1; i <= n; i++) {
        if (a[i] == n) {
            root = i;
        }
    }
    cout << dfs(root, 1, n) << '\n';
}       
signed main () {
    ios::sync_with_stdio(0); cin.tie(0);
    int tc = 1; //cin >> tc;
    while (tc--) solve();
}

• Subtask 1: 7 / 7
• Subtask 2: 7 / 7
• Subtask 3: 7 / 7
• Subtask 4: 0 / 10
• Subtask 5: 0 / 20
• Subtask 6: 0 / 23
• Subtask 7: 0 / 26