Submission #146986

#	Time	Username	Problem	Language	Result	Execution time	Memory
146986		jun6873	Lightning Rod (NOI18_lightningrod)	C++11	7 / 100	2060 ms	156500 KiB

Main

#include <bits/stdc++.h>
using namespace std;

using lint = long long;
using pint = pair<lint, lint>;
#define x first
#define y second

int n, k;
pint a[10000004], c[10000004];

int ccw(pint a, pint b, pint c) {
    lint k = a.x*b.y + b.x*c.y + c.x*a.y - b.x*a.y - c.x*b.y - a.x*c.y;
    if (k>0) return 1;
    if (k<0) return -1;
    return 0;
}

int main() {
    ios::sync_with_stdio(0); cin.tie(0);

    cin >> n;
    for (int i=0; i<n; i++) {
        int x, y;
        cin >> x >> y;
        a[i] = pint(x+y, y-x);
    }

    sort(a, a+n);

    c[k++] = a[0];

    for (int i=1; i<n; i++) {
        while (k>=2 and ccw(c[k-2], c[k-1], a[i]) >= 0) k--;
        c[k++] = a[i];
    }

    int ans = k;
    for (int i=0; i+1<k; i++) if (c[i].y <= c[i+1].y or c[i].x >= c[i+1].x) ans--;

    cout << ans << '\n';
}

• Subtask 1: 0 / 4
• Subtask 2: 7 / 7
• Subtask 3: 0 / 12
• Subtask 4: 0 / 21
• Subtask 5: 0 / 26
• Subtask 6: 0 / 10
• Subtask 7: 0 / 20