#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].empty())) {
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();
}
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
1 ms |
6744 KB |
Output is correct |
2 |
Incorrect |
1 ms |
6748 KB |
Output isn't correct |
3 |
Halted |
0 ms |
0 KB |
- |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
1 ms |
6744 KB |
Output is correct |
2 |
Incorrect |
1 ms |
6748 KB |
Output isn't correct |
3 |
Halted |
0 ms |
0 KB |
- |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
1 ms |
6744 KB |
Output is correct |
2 |
Incorrect |
1 ms |
6748 KB |
Output isn't correct |
3 |
Halted |
0 ms |
0 KB |
- |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
1 ms |
6744 KB |
Output is correct |
2 |
Incorrect |
1 ms |
6748 KB |
Output isn't correct |
3 |
Halted |
0 ms |
0 KB |
- |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
1 ms |
6744 KB |
Output is correct |
2 |
Incorrect |
1 ms |
6748 KB |
Output isn't correct |
3 |
Halted |
0 ms |
0 KB |
- |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
1 ms |
6748 KB |
Output is correct |
2 |
Incorrect |
1 ms |
6748 KB |
Output isn't correct |
3 |
Halted |
0 ms |
0 KB |
- |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
1 ms |
6744 KB |
Output is correct |
2 |
Incorrect |
1 ms |
6748 KB |
Output isn't correct |
3 |
Halted |
0 ms |
0 KB |
- |