HDU 4004 The Frog's Games(二分)

题目链接

题意理解的有些问题。

#include <iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
#define LL __int64
LL p[501001];
int n;
int judge(int x,int m)
{
    int pre = 0,num = 0,i;
    for(i = 0;i <= n;i ++)
    {
        if(p[i] - pre <= x)
        ;
        else
        {
            num ++;
            pre = p[i-1];
        }
    }
    if(num + 1 > m)
    return 0;
    else
    return 1;
}
int main()
{
    int m,i,l;
    LL str,mid,end,minz;
    while(scanf("%d%d%d",&l,&n,&m)!=EOF)
    {
        for(i = 0; i < n; i ++)
            scanf("%I64d",&p[i]);
        sort(p,p+n);
        if(n == 0||m == 1)
        {
            printf("%d
",l);
            continue;
        }
        p[n] = l;
        minz = p[0];
        for(i = 0;i < n;i ++)
        {
            minz = max(minz,p[i+1]-p[i]);
        }
        str = minz;end = l;
        while(str < end)
        {
            mid = (str+end)/2;
            if(judge(mid,m) == 0)
            str = mid + 1;
            else
            end = mid;
        }
        printf("%I64d
",str);
    }
    return 0;
}