Submission #672963

#	Time	Username	Problem	Language	Result	Execution time	Memory
672963		vuavisao	Lightning Rod (NOI18_lightningrod)	C++14	100 / 100	1773 ms	262144 KiB

Main

#include<bits/stdc++.h>
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#define ll long long
using namespace std;

const int N = 1e7 + 10;
const int INF = 2e9 + 10;

struct Point {
    int x = 0, y = 0;
    Point() {};
    Point(int _x, int _y) { x = _x; y = _y; };
};

int n;
Point p[N];

int pred[N], suf[N];
int res;

int32_t main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    if (fopen("NOI18_lightningrod.inp", "r")) {
        freopen("NOI18_lightningrod.inp", "r", stdin);
        freopen("NOI18_lightningrod.out", "w", stdout);
    }
    cin >> n;
    for(int i = 1; i <= n; ++ i) {
        int x, y; cin >> x >> y;
        p[i] = Point(x + y, x - y);
    }
    pred[0] = - INF;
    for(int i = 1; i <= n; ++ i) {
        pred[i] = max(pred[i - 1], p[i].x);
    }
    suf[n + 1] = INF;
    for(int i = n; i >= 1; -- i) {
        suf[i] = min(suf[i + 1], p[i].y);
    }
    for(int i = 1; i <= n; ++ i) {
        bool have_left = (pred[i] > pred[i - 1]);
        bool have_right = (suf[i] < suf[i + 1]);
        res += (have_left & have_right);
    }
    cout << res;
    return 0;
}

/// Code by vuavisao

Compilation message (stderr)

lightningrod.cpp: In function 'int32_t main()':
lightningrod.cpp:27:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   27 |         freopen("NOI18_lightningrod.inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
lightningrod.cpp:28:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   28 |         freopen("NOI18_lightningrod.out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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