Submission #133117

#	Time	Username	Problem	Language	Result	Execution time	Memory
133117		win11905	Mobile (BOI12_mobile)	C++11	0 / 100	257 ms	8704 KiB

mobile

#include <bits/stdc++.h>
#define pii pair<int, int>
#define x first
#define y second
using namespace std;

int n, k;
vector<pii> vec;

double dist(pii p, double x) {
    return hypot((double)p.x - x, (double)p.y);
}

double f(double x) { return x * x; }

double getx(pii p1, pii p2) {
    double x1 = p1.x, x2 = p2.x, y1 = p1.y, y2 = p2.y;
    return (f(x2) + f(y2) - f(x1) - f(y1)) / (2 * (x2 - x1));
}

int main() {
    scanf("%d %d", &n, &k);
    for(int i = 0, x, y; i < n; ++i) {
        scanf("%d %d", &x, &y);
        if(vec.empty()) vec.emplace_back(x, abs(y));
        else if(vec.back().x == x) vec.back().y = min(vec.back().y, abs(y));
        else vec.emplace_back(x, abs(y));
    }
    vector<pii> stk;
    stk.emplace_back(vec[0]), stk.emplace_back(vec[1]);
    for(int i = 2; i < vec.size(); ++i) {
        while(stk.size() >= 2 && getx(stk.back(), vec[i]) > getx(stk[stk.size()-2], vec[i])) stk.pop_back();
        stk.emplace_back(vec[i]);
    }
    double ans = 0;
    for(int i = 1; i < vec.size(); ++i) {
        double x = getx(vec[i], vec[i-1]);
        if(x >= 0 && x <= k) {
            ans = max(ans, dist(vec[i], x));
        }
    }
    printf("%.6f\n", ans);
}

Compilation message (stderr)

mobile.cpp: In function 'int main()':
mobile.cpp:31:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i = 2; i < vec.size(); ++i) {
                    ~~^~~~~~~~~~~~
mobile.cpp:36:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i = 1; i < vec.size(); ++i) {
                    ~~^~~~~~~~~~~~
mobile.cpp:22:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d %d", &n, &k);
     ~~~~~^~~~~~~~~~~~~~~~~
mobile.cpp:24:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d %d", &x, &y);
         ~~~~~^~~~~~~~~~~~~~~~~

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