Submission #282710

#	Time	Username	Problem	Language	Result	Execution time	Memory
282710		rqi	Bigger segments (IZhO19_segments)	C++14	100 / 100	81 ms	20364 KiB

segments

#include <bits/stdc++.h>
using namespace std;
 
typedef long long ll;
typedef long double ld;
typedef double db; 
typedef string str; 

typedef pair<int,int> pi;
typedef pair<ll,ll> pl; 
typedef pair<db,db> pd; 

typedef vector<int> vi; 
typedef vector<bool> vb; 
typedef vector<ll> vl; 
typedef vector<db> vd; 
typedef vector<str> vs; 
typedef vector<pi> vpi;
typedef vector<pl> vpl; 
typedef vector<pd> vpd; 

#define mp make_pair
#define f first
#define s second
#define sz(x) (int)(x).size()
#define all(x) begin(x), end(x)
#define rall(x) (x).rbegin(), (x).rend() 
#define sor(x) sort(all(x)) 
#define rsz resize
#define ins insert 
#define ft front() 
#define bk back()
#define pf push_front 
#define pb push_back
#define eb emplace_back 
#define lb lower_bound 
#define ub upper_bound 

#define FOR(i,a,b) for (int i = (a); i < (b); ++i)
#define F0R(i,a) FOR(i,0,a)
#define ROF(i,a,b) for (int i = (b)-1; i >= (a); --i)
#define R0F(i,a) ROF(i,0,a)
#define trav(a,x) for (auto& a: x)

const int MOD = 1e9+7; // 998244353;
const int MX = 2e5+5; 
const ll INF = 1e18; 
const ld PI = acos((ld)-1);
const int xd[4] = {1,0,-1,0}, yd[4] = {0,1,0,-1}; 
mt19937 rng((uint32_t)chrono::steady_clock::now().time_since_epoch().count()); 

template<class T> bool ckmin(T& a, const T& b) { 
    return b < a ? a = b, 1 : 0; }
template<class T> bool ckmax(T& a, const T& b) { 
    return a < b ? a = b, 1 : 0; } 
constexpr int pct(int x) { return __builtin_popcount(x); } 
constexpr int bits(int x) { return 31-__builtin_clz(x); } // floor(log2(x)) 
ll cdiv(ll a, ll b) { return a/b+((a^b)>0&&a%b); } // divide a by b rounded up
ll fdiv(ll a, ll b) { return a/b-((a^b)<0&&a%b); } // divide a by b rounded down
ll half(ll x) { return fdiv(x,2); }

template<class T, class U> T fstTrue(T lo, T hi, U f) { 
    // note: if (lo+hi)/2 is used instead of half(lo+hi) then this will loop infinitely when lo=hi
    hi ++; assert(lo <= hi); // assuming f is increasing
    while (lo < hi) { // find first index such that f is true 
        T mid = half(lo+hi);
        f(mid) ? hi = mid : lo = mid+1; 
    } 
    return lo;
}
template<class T, class U> T lstTrue(T lo, T hi, U f) {
    lo --; assert(lo <= hi); // assuming f is decreasing
    while (lo < hi) { // find first index such that f is true 
        T mid = half(lo+hi+1);
        f(mid) ? lo = mid : hi = mid-1;
    } 
    return lo;
}
template<class T> void remDup(vector<T>& v) { 
    sort(all(v)); v.erase(unique(all(v)),end(v)); }

// INPUT
template<class A> void re(complex<A>& c);
template<class A, class B> void re(pair<A,B>& p);
template<class A> void re(vector<A>& v);
template<class A, size_t SZ> void re(array<A,SZ>& a);

template<class T> void re(T& x) { cin >> x; }
void re(db& d) { str t; re(t); d = stod(t); }
void re(ld& d) { str t; re(t); d = stold(t); }
template<class H, class... T> void re(H& h, T&... t) { re(h); re(t...); }

template<class A> void re(complex<A>& c) { A a,b; re(a,b); c = {a,b}; }
template<class A, class B> void re(pair<A,B>& p) { re(p.f,p.s); }
template<class A> void re(vector<A>& x) { trav(a,x) re(a); }
template<class A, size_t SZ> void re(array<A,SZ>& x) { trav(a,x) re(a); }

// TO_STRING
#define ts to_string
str ts(char c) { return str(1,c); }
str ts(const char* s) { return (str)s; }
str ts(str s) { return s; }
str ts(bool b) { 
    #ifdef LOCAL
        return b ? "true" : "false"; 
    #else 
        return ts((int)b);
    #endif
}
template<class A> str ts(complex<A> c) { 
    stringstream ss; ss << c; return ss.str(); }
str ts(vector<bool> v) {
    str res = "{"; F0R(i,sz(v)) res += char('0'+v[i]);
    res += "}"; return res; }
template<size_t SZ> str ts(bitset<SZ> b) {
    str res = ""; F0R(i,SZ) res += char('0'+b[i]);
    return res; }
template<class A, class B> str ts(pair<A,B> p);
template<class T> str ts(T v) { // containers with begin(), end()
    #ifdef LOCAL
        bool fst = 1; str res = "{";
        for (const auto& x: v) {
            if (!fst) res += ", ";
            fst = 0; res += ts(x);
        }
        res += "}"; return res;
    #else
        bool fst = 1; str res = "";
        for (const auto& x: v) {
            if (!fst) res += " ";
            fst = 0; res += ts(x);
        }
        return res;

    #endif
}
template<class A, class B> str ts(pair<A,B> p) {
    #ifdef LOCAL
        return "("+ts(p.f)+", "+ts(p.s)+")"; 
    #else
        return ts(p.f)+" "+ts(p.s);
    #endif
}

// OUTPUT
template<class A> void pr(A x) { cout << ts(x); }
template<class H, class... T> void pr(const H& h, const T&... t) { 
    pr(h); pr(t...); }
void ps() { pr("\n"); } // print w/ spaces
template<class H, class... T> void ps(const H& h, const T&... t) { 
    pr(h); if (sizeof...(t)) pr(" "); ps(t...); }

// DEBUG
void DBG() { cerr << "]" << endl; }
template<class H, class... T> void DBG(H h, T... t) {
    cerr << ts(h); if (sizeof...(t)) cerr << ", ";
    DBG(t...); }
#ifdef LOCAL // compile with -DLOCAL, chk -> fake assert
    #define dbg(...) cerr << "Line(" << __LINE__ << ") -> [" << #__VA_ARGS__ << "]: [", DBG(__VA_ARGS__)
    #define chk(...) if (!(__VA_ARGS__)) cerr << "Line(" << __LINE__ << ") -> function(" \
         << __FUNCTION__  << ") -> CHK FAILED: (" << #__VA_ARGS__ << ")" << "\n", exit(0);
#else
    #define dbg(...) 0
    #define chk(...) 0
#endif

// FILE I/O
void setIn(str s) { freopen(s.c_str(),"r",stdin); }
void setOut(str s) { freopen(s.c_str(),"w",stdout); }
void unsyncIO() { cin.tie(0)->sync_with_stdio(0); }
void setIO(str s = "") {
    unsyncIO();
    // cin.exceptions(cin.failbit); 
    // throws exception when do smth illegal
    // ex. try to read letter into int
    if (sz(s)) { setIn(s+".in"), setOut(s+".out"); } // for USACO
}

const int mx = 500005;
int ans = 1;
ll a[mx];
ll pref[mx];
int dp[mx];
int ndp[mx];

int main() {
    setIO();
    int N;
    cin >> N;
    for(int i = 1; i <= N; i++){
        cin >> a[i];
        pref[i] = pref[i-1]+a[i];
    }
    dp[0] = -1;
    for(int i = 1; i <= N; i++){
        dp[i] = 0;
    }

    // for(int i = 0; i <= N; i++){
    //     cout << i << "\t";
    //     //dbg(i, dp[i], 2*pref[i]-pref[dp[i]]);
    // }
    // cout << "\n";

    //last level, this level
    int lvl2 = 0;
    deque<pair<ll, int>> d1; //pref >= f, want bigger s value, stored in decreasing s value & decreasing f value
    deque<pair<ll, int>> d2; //pref >= f, want bigger s value, stored in decreasing s value & decreasing f value
    d2.pb(mp(0, 0));
    for(int i = 1; i <= N; i++){
    	while(true){
    		if(sz(d1) <= 1 || pref[i] < d1[sz(d1)-2].f) break;
    		d1.pop_back();
    	}
    	while(true){
    		if(sz(d2) <= 1 || pref[i] < d2[sz(d2)-2].f) break;
    		d2.pop_back();
    	}
    	assert(sz(d2));
    	if(pref[i] >= d2.back().f){
    		dp[i] = d2.back().s;
    		lvl2++;
    		swap(d1, d2);
    		d2.clear();
    		pair<ll, int> val = mp(2*pref[i]-pref[dp[i]], i);
    		d2.pb(val);
    	}
    	else{
    		assert(sz(d1) && pref[i] >= d1.back().f);
    		dp[i] = d1.back().s;
    		pair<ll, int> val = mp(2*pref[i]-pref[dp[i]], i);
    		while(true){
    		    if(sz(d2) == 0 || val.f > d2.front().f) break;
    		    d2.pop_front();
    		}
    		d2.push_front(val);
    	}
    }
    ps(lvl2);

    // for(int t = 2; t <= N; t++){
    //     //dbg(t);
    //     deque<pair<ll, int>> d; //pref >= f, want bigger s value, stored in decreasing s value & decreasing f value
    //     for(int i = 0; i <= N; i++){
    //         //dbg(i, d);
    //         while(true){
    //             if(sz(d) <= 1 || pref[i] < d[sz(d)-2].f) break;
    //             d.pop_back();
    //         }
    //         if(sz(d) == 0 || pref[i] < d.bk.f){
    //             ndp[i] = -1;
    //         }
    //         else{
    //             ndp[i] = d.bk.s;
    //         }
    //         //dbg(i, d);
    //         if(dp[i] != -1){
    //             pair<ll, int> val = mp(2*pref[i]-pref[dp[i]], i);
    //             while(true){
    //                 if(sz(d) == 0 || val.f > d.front().f) break;
    //                 d.pop_front();
    //             }
    //             //dbg(i, d);
    //             d.push_front(val);
    //             //dbg(i, d);
    //         }
    //     }
        
    //     for(int i = 0; i <= N; i++){
    //         dp[i] = ndp[i];
    //         cout << dp[i] << "\t";
    //         //dbg(i, dp[i], 2*pref[i]-pref[dp[i]]);
    //     }
    //     cout << "\n";
    //     if(dp[N] != -1) ckmax(ans, t);
    // }
    // ps(ans);
    // you should actually read the stuff at the bottom
}

/* stuff you should look for
    * int overflow, array bounds
    * special cases (n=1?)
    * do smth instead of nothing and stay organized
    * WRITE STUFF DOWN
*/

Compilation message (stderr)

segments.cpp: In function 'void setIn(str)':
segments.cpp:168:28: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
  168 | void setIn(str s) { freopen(s.c_str(),"r",stdin); }
      |                     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~
segments.cpp: In function 'void setOut(str)':
segments.cpp:169:29: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
  169 | void setOut(str s) { freopen(s.c_str(),"w",stdout); }
      |                      ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 13 / 13
• Subtask 2: 14 / 14
• Subtask 3: 10 / 10
• Subtask 4: 36 / 36
• Subtask 5: 27 / 27