Submission #1163233

#	Time	Username	Problem	Language	Result	Execution time	Memory
1163233		SmuggingSpun	Bigger segments (IZhO19_segments)	C++20	100 / 100	143 ms	35836 KiB

segments

#include<bits/stdc++.h>
#define taskname "B"
using namespace std;
typedef long long ll;
const int INF = 1e9;
const ll LINF = 1e18;
template<class T>void maximize(T& a, T b){
    if(a < b){
        a = b;
    }
}
int n;
namespace sub123{
    void solve(){
        vector<ll>f(n + 1);
        f[0] = 0;
        for(int i = 1; i <= n; i++){
            cin >> f[i];
            f[i] += f[i - 1];
        }
        vector<vector<int>>dp(n + 1, vector<int>(n + 1, -INF));
        for(int l = dp[1][1] = 1; l < n; l++){
            for(int r = l; r < n; r++){
                maximize(dp[l][r + 1], dp[l][r]);
                int low = r + 1, high = n, p = -1;
                while(low <= high){
                    int mid = (low + high) >> 1;
                    if(f[mid] - f[r] >= f[r] - f[l - 1]){
                        high = (p = mid) - 1;
                    }
                    else{
                        low = mid + 1;
                    }
                }                
                if(p != -1){
                    maximize(dp[r + 1][p], dp[l][r] + 1);
                }
            }
        }
        int ans = 0;
        for(int i = 1; i <= n; i++){
            maximize(ans, dp[i][n]);
        }
        cout << ans;
    }
}
namespace sub45{
    const int lim = 5e5 + 5;
    ll a[lim];
    int dp[lim], pre[lim];
    void solve(){
        memset(pre, a[0] = dp[0] = 0, sizeof(pre));
        for(int i = 1; i <= n; i++){
            cin >> a[i];
            a[i] += a[i - 1];
        }
        a[n + 1] = LINF;
        for(int i = 1; i <= n; i++){
            maximize(pre[i], pre[i - 1]);
            dp[i] = dp[pre[pre[lower_bound(a + i + 1, a + n + 2, (a[i] << 1LL) - a[pre[i]]) - a] = i]] + 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 <= 3000){
        sub123::solve();
    }
    else{
        sub45::solve();
    }
}

Compilation message (stderr)

segments.cpp: In function 'int main()':
segments.cpp:68:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   68 |         freopen(taskname".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~

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