#pragma GCC optimize ("O3")
#pragma GCC target ("sse4")
#include <bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/rope>
using namespace std;
using namespace __gnu_pbds;
using namespace __gnu_cxx;
typedef long long ll;
typedef long double ld;
typedef complex<ld> cd;
typedef pair<int, int> pi;
typedef pair<ll,ll> pl;
typedef pair<ld,ld> pd;
typedef vector<int> vi;
typedef vector<ld> vd;
typedef vector<ll> vl;
typedef vector<pi> vpi;
typedef vector<pl> vpl;
typedef vector<cd> vcd;
template <class T> using Tree = tree<T, null_type, less<T>, rb_tree_tag,tree_order_statistics_node_update>;
#define FOR(i, a, b) for (int i = (a); i < (b); i++)
#define F0R(i, a) for (int i = 0; i < (a); i++)
#define FORd(i,a,b) for (int i = (b)-1; i >= (a); i--)
#define F0Rd(i,a) for (int i = (a)-1; i >= 0; i--)
#define trav(a, x) for (auto& a : x)
#define mp make_pair
#define pb push_back
#define f first
#define s second
#define lb lower_bound
#define ub upper_bound
#define sz(x) (int)x.size()
#define all(x) begin(x), end(x)
#define rsz resize
const int MOD = 1000000007; // 998244353
const ll INF = 1e18;
const int MX = 500005;
const ld PI = 4*atan((ld)1);
template<class T> void ckmin(T &a, T b) { a = min(a, b); }
template<class T> void ckmax(T &a, T b) { a = max(a, b); }
namespace input {
template<class T> void re(complex<T>& x);
template<class T1, class T2> void re(pair<T1,T2>& p);
template<class T> void re(vector<T>& a);
template<class T, size_t SZ> void re(array<T,SZ>& a);
template<class T> void re(T& x) { cin >> x; }
void re(double& x) { string t; re(t); x = stod(t); }
void re(ld& x) { string t; re(t); x = stold(t); }
template<class Arg, class... Args> void re(Arg& first, Args&... rest) {
re(first); re(rest...);
}
template<class T> void re(complex<T>& x) { T a,b; re(a,b); x = cd(a,b); }
template<class T1, class T2> void re(pair<T1,T2>& p) { re(p.f,p.s); }
template<class T> void re(vector<T>& a) { F0R(i,sz(a)) re(a[i]); }
template<class T, size_t SZ> void re(array<T,SZ>& a) { F0R(i,SZ) re(a[i]); }
}
using namespace input;
namespace output {
template<class T1, class T2> void pr(const pair<T1,T2>& x);
template<class T, size_t SZ> void pr(const array<T,SZ>& x);
template<class T> void pr(const vector<T>& x);
template<class T> void pr(const set<T>& x);
template<class T1, class T2> void pr(const map<T1,T2>& x);
template<class T> void pr(const T& x) { cout << x; }
template<class Arg, class... Args> void pr(const Arg& first, const Args&... rest) {
pr(first); pr(rest...);
}
template<class T1, class T2> void pr(const pair<T1,T2>& x) {
pr("{",x.f,", ",x.s,"}");
}
template<class T> void prContain(const T& x) {
pr("{");
bool fst = 1; for (const auto& a: x) pr(!fst?", ":"",a), fst = 0; // const needed for vector<bool>
pr("}");
}
template<class T, size_t SZ> void pr(const array<T,SZ>& x) { prContain(x); }
template<class T> void pr(const vector<T>& x) { prContain(x); }
template<class T> void pr(const set<T>& x) { prContain(x); }
template<class T1, class T2> void pr(const map<T1,T2>& x) { prContain(x); }
void ps() { pr("\n"); }
template<class Arg> void ps(const Arg& first) {
pr(first); ps(); // no space at end of line
}
template<class Arg, class... Args> void ps(const Arg& first, const Args&... rest) {
pr(first," "); ps(rest...); // print w/ spaces
}
}
using namespace output;
namespace io {
void setIn(string s) { freopen(s.c_str(),"r",stdin); }
void setOut(string s) { freopen(s.c_str(),"w",stdout); }
void setIO(string s = "") {
ios_base::sync_with_stdio(0); cin.tie(0); // fast I/O
if (sz(s)) { setIn(s+".in"), setOut(s+".out"); } // for USACO
}
}
using namespace io;
template<class T> T invGeneral(T a, T b) {
a %= b; if (a == 0) return b == 1 ? 0 : -1;
T x = invGeneral(b,a);
return x == -1 ? -1 : ((1-(ll)b*x)/a+b)%b;
}
template<class T> struct modular {
T val;
explicit operator T() const { return val; }
modular() { val = 0; }
modular(const ll& v) {
val = (-MOD <= v && v <= MOD) ? v : v % MOD;
if (val < 0) val += MOD;
}
// friend ostream& operator<<(ostream& os, const modular& a) { return os << a.val; }
friend void pr(const modular& a) { pr(a.val); }
friend void re(modular& a) { ll x; re(x); a = modular(x); }
friend bool operator==(const modular& a, const modular& b) { return a.val == b.val; }
friend bool operator!=(const modular& a, const modular& b) { return !(a == b); }
friend bool operator<(const modular& a, const modular& b) { return a.val < b.val; }
modular operator-() const { return modular(-val); }
modular& operator+=(const modular& m) { if ((val += m.val) >= MOD) val -= MOD; return *this; }
modular& operator-=(const modular& m) { if ((val -= m.val) < 0) val += MOD; return *this; }
modular& operator*=(const modular& m) { val = (ll)val*m.val%MOD; return *this; }
friend modular pow(modular a, ll p) {
modular ans = 1; for (; p; p /= 2, a *= a) if (p&1) ans *= a;
return ans;
}
friend modular inv(const modular& a) {
auto i = invGeneral(a.val,MOD); assert(i != -1);
return i;
} // equivalent to return exp(b,MOD-2) if MOD is prime
modular& operator/=(const modular& m) { return (*this) *= inv(m); }
friend modular operator+(modular a, const modular& b) { return a += b; }
friend modular operator-(modular a, const modular& b) { return a -= b; }
friend modular operator*(modular a, const modular& b) { return a *= b; }
friend modular operator/(modular a, const modular& b) { return a /= b; }
};
typedef modular<int> mi;
typedef pair<mi,mi> pmi;
typedef vector<mi> vmi;
typedef vector<pmi> vpmi;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
int N;
ll sum[MX];
map<int,int> dp[MX];
int main() {
setIO(); re(N);
FOR(i,1,N+1) {
re(sum[i]);
sum[i] += sum[i-1];
// ps("??",i,sum[i]);
}
dp[1][0] = dp[1][1] = 0;
FOR(i,1,N) {
if (i) trav(t,dp[i-1]) ckmax(dp[i][t.f],t.s);
// while (sz(dp[i]) > 2) dp[i].erase(dp[i].begin());
/*if (!sz(dp[i])) {
ps("??",i);
exit(0);
}*/
trav(t,dp[i]) {
int it = lb(sum,sum+N+1,2*sum[i]-sum[t.s])-sum;
// ps("HUH",i,t.f,t.s,it,2*sum[i]-sum[t.f]);
if (it <= N) ckmax(dp[it][t.f+1],i);
}
}
// exit(0);
while (sz(dp[N]) > 1) dp[N].erase(dp[N].begin());
ps(dp[N].begin()->f);
// dp[pos][ans] -> max index
// upd dp[min pos such that sum[pos] >= 2*sum[ans]-sum[max index]][ans+1] -> pos
}
/* stuff you should look for
* int overflow, array bounds
* special cases (n=1?), set tle
* do smth instead of nothing and stay organized
*/
Compilation message
segments.cpp: In function 'void io::setIn(std::__cxx11::string)':
segments.cpp:113:35: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
void setIn(string s) { freopen(s.c_str(),"r",stdin); }
~~~~~~~^~~~~~~~~~~~~~~~~~~~~
segments.cpp: In function 'void io::setOut(std::__cxx11::string)':
segments.cpp:114:36: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
void setOut(string s) { freopen(s.c_str(),"w",stdout); }
~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
23 ms |
23800 KB |
Output is correct |
| 2 |
Correct |
23 ms |
23804 KB |
Output is correct |
| 3 |
Correct |
23 ms |
23800 KB |
Output is correct |
| 4 |
Incorrect |
23 ms |
23932 KB |
Output isn't correct |
| 5 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
23 ms |
23800 KB |
Output is correct |
| 2 |
Correct |
23 ms |
23804 KB |
Output is correct |
| 3 |
Correct |
23 ms |
23800 KB |
Output is correct |
| 4 |
Incorrect |
23 ms |
23932 KB |
Output isn't correct |
| 5 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
23 ms |
23800 KB |
Output is correct |
| 2 |
Correct |
23 ms |
23804 KB |
Output is correct |
| 3 |
Correct |
23 ms |
23800 KB |
Output is correct |
| 4 |
Incorrect |
23 ms |
23932 KB |
Output isn't correct |
| 5 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
23 ms |
23800 KB |
Output is correct |
| 2 |
Correct |
23 ms |
23804 KB |
Output is correct |
| 3 |
Correct |
23 ms |
23800 KB |
Output is correct |
| 4 |
Incorrect |
23 ms |
23932 KB |
Output isn't correct |
| 5 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
23 ms |
23800 KB |
Output is correct |
| 2 |
Correct |
23 ms |
23804 KB |
Output is correct |
| 3 |
Correct |
23 ms |
23800 KB |
Output is correct |
| 4 |
Incorrect |
23 ms |
23932 KB |
Output isn't correct |
| 5 |
Halted |
0 ms |
0 KB |
- |
