Submission #628242

#	Time	Username	Problem	Language	Result	Execution time	Memory
628242		duytuandao21	Bigger segments (IZhO19_segments)	C++17	37 / 100	761 ms	93120 KiB

segments

#include<iostream>
#include<cmath>
#include<algorithm>
#include<stack>
using namespace std;
#define MASK(i) (1LL << (i))
#define BIT(x, i) (((x) >> (i)) & 1)
#define fi first
#define se second
#define ll long long
#define mp make_pair
#define pb push_back
#define ii pair<int, int>
#define task "test"
 
const int inf = 1e9 + 7;
const ll infll = (ll)1e18 + 7;
const int MOD = 1e9 + 7;
const int N = 2e6 + 3;
 
template <typename T1, typename T2> bool minimize(T1 &a, T2 b){if (a > b) {a = b; return true;} return false;}
template <typename T1, typename T2> bool maximize(T1 &a, T2 b){if (a < b) {a = b; return true;} return false;}
 
int n;
ll a[N], dp[3005][3005], dp1[3005][3005], bit[3005][3005];
 
void update(int x,int y,int val) {
    while(x <= n) {
        maximize(bit[x][y], val);
        x += (x & -x);
    }
}
ll get(int y,int l,int r) {
    int ans = -inf;
    while(l <= r) {
        if(r - (r & -r) >= l) {
            maximize(ans, bit[r][y]);
            r -= (r & -r);
        } else {
            maximize(ans, dp1[r][y]);
            r--;
        }
    }
    return ans;
}
void sol1() {
    for(int i=1;i<=n;i++) {
        for(int j=1;j<=i;j++) {
            if(j == 1) {
                dp1[j][i] = 1;
                update(j, i, dp1[j][i]);
                continue;
            }
            ll sum = a[i] - a[j-1];
            //for(int k=1;k<j;k++) {
                //ll preSum = a[j-1] - a[k-1];
                //if(preSum <= sum) maximize(dp[j][i], dp[k][j-1] + 1);
            //}
            int l = 1;
            int r = j - 1;
            int pos = -1;
            while(l <= r) {
                int mid = (l + r) / 2;
                if(a[j-1] - a[mid - 1] <= sum) {
                    pos = mid;
                    r = mid - 1;
                } else l = mid + 1;
            }
            //cout<<j<<" "<<i<<" "<<pos<<'\n';
			if(pos != -1) {
				int x = get(j-1, pos, j-1);
				if(x != 0) dp1[j][i] = x + 1;
			}
            // if(pos != -1) dp1[j][i] = get(j-1, pos, j-1) + 1;
            // maximize(dp1[j][i], 0);
            if(dp1[j][i] == 0) dp1[j][i] = -inf;
            update(j, i, dp1[j][i]);
        }
    }
    ll ans = 0;
    for(int i=1;i<=n;i++) maximize(ans, dp1[i][n]);
    cout<<ans;
}
int main()
{
	ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
	cin>>n;
    for(int i=1;i<=n;i++) {
        cin>>a[i];
        a[i] += a[i-1];
    }
    // for(int i=1;i<=n;i++) {
    //     for(int j=1;j<=i;j++) {
    //         if(j == 1) {
    //             dp[j][i] = 1;
    //             continue;
    //         }
    //         ll sum = a[i] - a[j-1];
    //         for(int k=j-1;k>0;k--) {
    //             ll preSum = a[j-1] - a[k-1];
    //             if(preSum <= sum) maximize(dp[j][i], dp[k][j-1] + 1); else break;
    //         }
    //         if(dp[j][i] == 0) dp[j][i] = -inf;
    //     }
    // }
    // ll res = 0;
    // for(int i=1;i<=n;i++) maximize(res, dp[i][n]);
    // cout<<res;
	sol1();
    return 0;
}
 
/* 10
4 1 2 4 2 3 5 6 8 10 */

• Subtask 1: 13 / 13
• Subtask 2: 14 / 14
• Subtask 3: 10 / 10
• Subtask 4: 0 / 36
• Subtask 5: 0 / 27