Submission #37821

#	Time	Username	Problem	Language	Result	Execution time	Memory
37821		Just_Solve_The_Problem	Divide and conquer (IZhO14_divide)	C++11	48 / 100	146 ms	5920 KiB

divide

#include <bits/stdc++.h>

using namespace std;

#define ll long long

const int N = (int)1e5 + 7;

ll x[N], g[N], d[N];
ll pg[N], pd[N];
int n;
ll ans = 0;

bool check (int l, int r) {
    return x[r] - x[l] <= pd[r] - pd[l - 1];
}

void slow () {
    int cnt = 0;
    for (int i = 1; i <= min(n, 10000); i++) {
        if (pg[n] - pg[i - 1] <= ans) continue;
        for (int j = i; j <= min(n, 10000); j++) {
            if (check(i, j)) {
                ans = max(ans, pg[j] - pg[i - 1]);
            }
        }
    }
}

void fast () {
    int l = 1;
    int r = 1;
    do {
//        cout << l << ' ' << r << endl;
        if (check(l, r)) {
            ans = max(ans, pg[r] - pg[l - 1]);
            if (l > 1 && check(l - 1, r)) {
                l--;
            } else {
                if (r == n) {
                    break;
                }
                r++;
            }
        } else {
            l++;
        }
        r = min(r, n);
        l = min(l, r + 1);
    } while (r != n || l != n);

    l = n;
    r = n;
    do {
        if (check(l, r)) {
            ans = max(ans, pg[r] - pg[l - 1]);
            if (r < n && check(l, r + 1)) {
                r++;
            } else {
                if (l == 1) {
                    break;
                }
                l--;
            }
        } else {
            r--;
        }
        l = max(l, 1);
        r = max(l, r);
    } while (r != 1 || l != 1);
}

main () {
    scanf ("%d", &n);
    for (int i = 1; i <= n; i++) {
        scanf ("%lld %lld %lld", x + i, g + i, d + i);
        ans = max(ans, g[i]);
    }
    for (int i = 1; i <= n; i++) {
        pg[i] = pg[i - 1] + g[i];
        pd[i] = pd[i - 1] + d[i];
    }
    if (n <= 5000) {
        slow();
    } else {
        slow();
        fast();
    }
    cout << ans;
}

Compilation message (stderr)

divide.cpp: In function 'void slow()':
divide.cpp:19:9: warning: unused variable 'cnt' [-Wunused-variable]
     int cnt = 0;
         ^
divide.cpp: At global scope:
divide.cpp:73:7: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
 main () {
       ^
divide.cpp: In function 'int main()':
divide.cpp:74:21: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf ("%d", &n);
                     ^
divide.cpp:76:54: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf ("%lld %lld %lld", x + i, g + i, d + i);
                                                      ^

• Subtask 1: 17 / 17
• Subtask 2: 31 / 31
• Subtask 3: 0 / 52