#include<bits/stdc++.h>
#define taskname "B"
using namespace std;
template<class T>void minimize(T& a, T b){
if(a > b){
a = b;
}
}
int n;
namespace sub12{
void solve(){
vector<int>a(n);
for(int& x : a){
cin >> x;
}
int ans = n;
for(int mask = (1 << (n - 1)) - 2; mask > -1; mask--){
vector<pair<int, int>>range(1, make_pair(0, 0));
bool flag = true;
for(int i = 1; i < n; i++){
if(1 << (i - 1) & mask){
range.emplace_back(i, i);
}
else{
if(a[i] < a[range.back().second]){
flag = false;
break;
}
range.back().second = i;
}
}
if(flag && range.size() < ans){
vector<int>b;
for(auto& [l, r] : range){
if(b.empty()){
b = vector<int>(a.begin() + l, a.begin() + r + 1);
continue;
}
if(a[r] <= b[0]){
b.insert(b.begin(), a.begin() + l, a.begin() + r + 1);
}
else if(a[l] >= b.back()){
b.insert(b.end(), a.begin() + l, a.begin() + r + 1);
}
else{
flag = false;
for(int i = 0; i + 1 < b.size() && !flag; i++){
if(b[i] <= a[l] && b[i + 1] >= a[r]){
b.insert(b.begin() + i + 1, a.begin() + l, a.begin() + r + 1);
flag = true;
}
}
if(!flag){
break;
}
}
}
if(flag){
ans = range.size();
}
}
}
cout << ans;
}
}
namespace sub3{
void solve(){
vector<int>a(n + 1), dp(n + 1, n);
for(int i = 1; i <= n; i++){
cin >> a[i];
}
vector<vector<int>>b(n + 1);
for(int i = 1; i <= n; i++){
b[i] = b[i - 1];
b[i].emplace_back(a[i]);
for(int j = int(b[i].size() - 1); j > 0 && b[i][j] < b[i][j - 1]; j--){
swap(b[i][j], b[i][j - 1]);
}
}
dp[0] = 0;
for(int i = 1; i <= n; i++){
for(int j = i; j > 0; j--){
if(j < i && a[j] > a[j + 1]){
break;
}
if(b[j - 1].empty() || b[j - 1][0] >= a[i] || b[j - 1].back() <= a[j] || b[j - 1][upper_bound(b[j - 1].begin(), b[j - 1].end(), a[j]) - b[j - 1].begin()] >= a[i]){
minimize(dp[i], dp[j - 1] + 1);
}
}
}
cout << dp[n];
}
}
namespace sub4{
const int lim = 1e6 + 5;
const int INF = 1e9;
int a[lim], right[lim], left[lim], dp[lim];
void solve(){
set<int>s;
s.insert(right[left[0] = a[0] = dp[0] = 0] = INF);
for(int i = 1; i <= n; i++){
cin >> a[i];
left[i] = (a[i] >= a[i - 1] ? left[i - 1] : i);
}
for(int i = 1; i < n; i++){
s.insert(a[i]);
right[i] = *s.upper_bound(a[i + 1]);
}
for(int i = 1; i <= n; i++){
int low = left[i], high = i, p;
while(low <= high){
int mid = (low + high) >> 1;
if(right[mid - 1] >= a[i]){
high = (p = mid) - 1;
}
else{
low = mid + 1;
}
}
dp[i] = dp[p - 1] + 1;
}
cout << dp[n];
}
}
int main(){
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
if(fopen(taskname".inp", "r")){
freopen(taskname".inp", "r", stdin);
}
cin >> n;
if(n <= 20){
sub12::solve();
}
else if(n <= 300){
sub3::solve();
}
else{
sub4::solve();
}
}
컴파일 시 표준 에러 (stderr) 메시지
money.cpp: In function 'int main()':
money.cpp:128:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
128 | freopen(taskname".inp", "r", stdin);
| ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
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