// #define DEBUG
#include <iostream>
#include <map>
#ifdef DEBUG
#include <iomanip>
#endif
const int MAX = 1000005;
const int MAXK = 20;
int A[MAX * 2];
int N[MAX * 2][MAXK];
int solve(int i, int n, int k) {
if (i >= n) return 0;
if (k < 0) return 0;
int ni = N[i][k];
if (ni < n)
return solve(ni, n, k - 1) + (1 << k);
else
return solve(i, n, k - 1);
}
int main() {
std::ios_base::sync_with_stdio(0);
int n;
std::cin >> n;
for (int i = 0; i < n; ++i) std::cin >> A[i];
for (int i = 0; i < n; ++i) A[i + n] = A[i];
std::map<int, int> M;
A[2*n] = MAX;
M[MAX] = 2 * n;
for (int i = 0; i < MAXK; ++i) N[2*n][i] = 2*n;
for (int i = 2 * n - 1; i >= 0; --i) {
while (M.begin()->first <= A[i]) M.erase(M.begin());
N[i][0] = M.begin()->second;
for (int k = 1; k < MAXK; ++k) N[i][k] = N[N[i][k - 1]][k - 1];
M[A[i]] = i;
}
#ifdef DEBUG
for (int i = 0; i <= 2 * n; ++i) {
std::clog << std::setw(4) << i;
}
std::clog << std::endl;
for (int i = 0; i <= 2 * n; ++i) {
std::clog << std::setw(4) << (A[i] < MAX ? A[i] : -1);
}
std::clog << std::endl;
for (int i = 0; i <= 2 * n; ++i) {
std::clog << std::setw(4) << N[i][0];
}
std::clog << std::endl;
#endif
int best = 0;
for (int i = 0; i < n; ++i) {
best = std::max(best, solve(i, i + n, MAXK - 1)+1);
}
std::cout << best << std::endl;
return 0;
}
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 57 58 59 60 61 62 | // #define DEBUG #include <iostream> #include <map> #ifdef DEBUG #include <iomanip> #endif const int MAX = 1000005; const int MAXK = 20; int A[MAX * 2]; int N[MAX * 2][MAXK]; int solve(int i, int n, int k) { if (i >= n) return 0; if (k < 0) return 0; int ni = N[i][k]; if (ni < n) return solve(ni, n, k - 1) + (1 << k); else return solve(i, n, k - 1); } int main() { std::ios_base::sync_with_stdio(0); int n; std::cin >> n; for (int i = 0; i < n; ++i) std::cin >> A[i]; for (int i = 0; i < n; ++i) A[i + n] = A[i]; std::map<int, int> M; A[2*n] = MAX; M[MAX] = 2 * n; for (int i = 0; i < MAXK; ++i) N[2*n][i] = 2*n; for (int i = 2 * n - 1; i >= 0; --i) { while (M.begin()->first <= A[i]) M.erase(M.begin()); N[i][0] = M.begin()->second; for (int k = 1; k < MAXK; ++k) N[i][k] = N[N[i][k - 1]][k - 1]; M[A[i]] = i; } #ifdef DEBUG for (int i = 0; i <= 2 * n; ++i) { std::clog << std::setw(4) << i; } std::clog << std::endl; for (int i = 0; i <= 2 * n; ++i) { std::clog << std::setw(4) << (A[i] < MAX ? A[i] : -1); } std::clog << std::endl; for (int i = 0; i <= 2 * n; ++i) { std::clog << std::setw(4) << N[i][0]; } std::clog << std::endl; #endif int best = 0; for (int i = 0; i < n; ++i) { best = std::max(best, solve(i, i + n, MAXK - 1)+1); } std::cout << best << std::endl; return 0; } |
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