Submission #1300839

#	Time	Username	Problem	Language	Result	Execution time	Memory
1300839		baotoan655	Sparklers (JOI17_sparklers)	C++20	100 / 100	17 ms	1752 KiB

sparklers

#include <bits/stdc++.h>
#define file(name)  if (fopen(name".inp", "r")) { freopen(name".inp", "r", stdin); freopen(name".out", "w", stdout); }
using namespace std;

const int N = 1e5 + 5;
int n, k, T;
int X[N];
long long val[N];

bool chk(int S) {
    for(int i = 1; i <= n; ++i) {
        val[i] = 2LL * S * i * T - X[i];
    }
    int curL = k, curR = k;
    int nl = k - 1, nr = k + 1;
    bool ok = true;
    while(ok) {
        ok = false;
        while(nl > 1 && val[nl] > val[curL] && val[nl] <= val[curR]) --nl;
        while(nr < n && val[curR] > val[nr] && val[curL] <= val[nr]) ++nr;
        if(nl >= 1 && val[nl] <= val[curL]) {
            curL = nl;
            --nl;
            ok = true;
        }
        if(nr <= n && val[curR] <= val[nr]) {
            curR = nr;
            ++nr;
            ok = true;
        }
    }
    if(nr <= n && val[curL] > val[nr]) return false;
    if(nl >= 1 && val[curR] < val[nl]) return false;
    int l = 1, r = n;
    nl = 2, nr = n - 1;
    ok = true;

    while(ok) {
        ok = false;
        while(val[nl] > val[l] && val[nl] <= val[r] && nl < k) ++nl;
        while(val[nr] < val[r] && val[nr] >= val[l] && nr > k) --nr;
        if(nl <= k && val[nl] <= val[l]) {
            l = nl;
            ++nl;
            ok = true;
        }
        if(nr >= k && val[nr] >= val[r]) {
            r = nr;
            --nr;
            ok = true;
        }
    }
    return curL <= l && r <= curR;
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0), cout.tie(0);

    file("A") else file("task");
    cin >> n >> k >> T;
    for(int i = 1; i <= n; ++i) cin >> X[i];
    int l = 0, r = 1e9, mid, res = -1;
    while(l <= r) {
        mid = (l + r) >> 1;
        if(chk(mid)) r = (res = mid) - 1;
        else l = mid + 1;
    }
    cout << res << '\n';
    return 0;
}

Compilation message (stderr)

sparklers.cpp: In function 'int main()':
sparklers.cpp:2:58: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
    2 | #define file(name)  if (fopen(name".inp", "r")) { freopen(name".inp", "r", stdin); freopen(name".out", "w", stdout); }
      |                                                   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
sparklers.cpp:60:5: note: in expansion of macro 'file'
   60 |     file("A") else file("task");
      |     ^~~~
sparklers.cpp:2:91: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
    2 | #define file(name)  if (fopen(name".inp", "r")) { freopen(name".inp", "r", stdin); freopen(name".out", "w", stdout); }
      |                                                                                    ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
sparklers.cpp:60:5: note: in expansion of macro 'file'
   60 |     file("A") else file("task");
      |     ^~~~
sparklers.cpp:2:58: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
    2 | #define file(name)  if (fopen(name".inp", "r")) { freopen(name".inp", "r", stdin); freopen(name".out", "w", stdout); }
      |                                                   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
sparklers.cpp:60:20: note: in expansion of macro 'file'
   60 |     file("A") else file("task");
      |                    ^~~~
sparklers.cpp:2:91: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
    2 | #define file(name)  if (fopen(name".inp", "r")) { freopen(name".inp", "r", stdin); freopen(name".out", "w", stdout); }
      |                                                                                    ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
sparklers.cpp:60:20: note: in expansion of macro 'file'
   60 |     file("A") else file("task");
      |                    ^~~~

• Subtask 1: 30 / 30
• Subtask 2: 20 / 20
• Subtask 3: 50 / 50