time-limit

D.bc.cpp

#include <stdio.h>
#include <float.h>

using namespace std;

bool isUpper(double t, int[] s, int[] v) {

    double m = FLT_MIN;

    for (int i = 0; i < n; ++i)
    {
        if (v[i] < 0)
        {
            if (s[i] + v[i] * t <= m)
                return true;
        }
        else
            m = max(m, s[i] + v[i] * t);
    }
    return false;
}

int main()
{
    int n;
    scanf("%d", &n);

    int v [n];
    int s [n];

    double l = 0;
    double h = 10000000000;
    double m;

    bool isNegative;
    bool isPositive;

    for (int i = 0; i < n; ++i)
    {
        scanf("%d %d", &s[i], &v[i]);
        if (v[i] > 0)
            isPositive = true;
        if (v[i] < 0 && isPositive)
            isNegative = true;
    }

    if ( !isNegative )
    {
        printf("-1.0000000000");
        return 0;
    }

    while (fabs(h-l) > 0.0000000001)
    {
        m = (h-l) / 2.0;

        if ( isUpper(m, s, v) )
            h = m;
        else
            l = m;
    }

    printf("%.10f", minimum);
    return 0;
}