HDU 4932 Miaomiao's Geometry（BestCoder Round #4）

#include<stdio.h>
#include<string.h>
#include<math.h>
#include<stdlib.h>
#include<queue>
#include<algorithm>
using namespace std;

const int N=1e5+10;
const int M=50000;
const int INF=0x3f3f3f3f;

double a[100], b[200]; ///b数组保存两点之间的长度及其一半
int n;

int Judge(double d) ///判断d能不能当满足条件的片段长度
{
    double p = a[0];
    int i;

    for (i = 1; i < n; i++)
    {
        if (fabs(p-a[i]) < 1e-9) continue;

        if (p > a[i]) return 0;
        else if (p+d <= a[i]) p = a[i];
        else p = a[i]+d;
    }

    return 1;
}

int main ()
{
    double Max;
    int T, i, k;

    scanf("%d", &T);

    while (T--)
    {
        scanf("%d", &n);
        for (i = 0; i < n; i++)
            scanf("%lf", &a[i]);

        memset(b, 0, sizeof(b));
        Max = -INF;
        k = 0;

        sort(a, a+n);

        for (i = 1; i < n; i++)
        {
            b[k++] = a[i]-a[i-1];
            b[k++] = (a[i]-a[i-1])/2;
        }

        for (i = 0; i < k; i++)
        {
            if (Judge(b[i]))
                Max = max(Max, b[i]);
        }

        printf("%.3f\n", Max);
    }

    return 0;
}