HDU 5037

最新推荐文章于 2017-09-07 17:22:43 发布

原创最新推荐文章于 2017-09-07 17:22:43 发布 · 722 阅读

0 ·

CC 4.0 BY-SA版权

文章标签：

#贪心

HDUOJ 同时被 3 个专栏收录

52 篇文章

订阅专栏

值得一做

46 篇文章

订阅专栏

-------- 其他专题 --------

24 篇文章

订阅专栏

一道贪心的题目，由于前后关系考虑需要细心一些，所以纠结了我好久！

总之，一道很好的贪心题。不过要注意，所有的石头都在整数点上，这点题目没交代清楚。

贴组数据（来源：http://blog.youkuaiyun.com/u011032846/article/details/39496587）：

3
4 17 3
4 7 12 16
4 18 3
4 7 12 16
4 19 3
4 7 12 16

代码（C++）：

#include <cstdio>
#include <iostream>
#include <algorithm>

#define MAX 200009
using namespace std;

int point[MAX];

int main()
{
    //freopen("in.txt","r",stdin);

    int t,n,m,len,ca,i,now,res,tmp,pre,d;
    scanf("%d",&t);
    for(ca=1;ca<=t;ca++)
    {
        scanf("%d %d %d",&n,&m,&len);
        for(i=0;i<n;i++) scanf("%d",&point[i]);
        sort(point,point+n);
        point[n]=m;
        now=0;
        res=0;
        pre=-len;
        for(i=0;i<=n;i++)
        {
            if(i<n&&point[i]-now<=len&&point[i+1]-now>len)
            {
                res++;
                pre=now;
                now=point[i];
            }else if(point[i]-now>len)
            {
                 tmp=(point[i]-now)/(len+1);
                 res+=tmp*2-1;
                 d=now-pre;
                 now+=tmp*(len+1)-d;
                 pre=now-(len+1-d);
                 i--;
            }
        }
        if(now<point[n]) res++;
        printf("Case #%d: %d\n",ca,res);
    }
    return 0;
}

题目（ http://acm.hdu.edu.cn/showproblem.php?pid=5037）：

Frog

Time Limit: 3000/1500 MS (Java/Others) Memory Limit: 262144/262144 K (Java/Others)

Problem Description

Once upon a time, there is a little frog called Matt. One day, he came to a river.

The river could be considered as an axis.Matt is standing on the left bank now (at position 0). He wants to cross the river, reach the right bank (at position M). But Matt could only jump for at most L units, for example from 0 to L.

As the God of Nature, you must save this poor frog.There are N rocks lying in the river initially. The size of the rock is negligible. So it can be indicated by a point in the axis. Matt can jump to or from a rock as well as the bank.

You don't want to make the things that easy. So you will put some new rocks into the river such that Matt could jump over the river in maximal steps.And you don't care the number of rocks you add since you are the God.

Note that Matt is so clever that he always choose the optimal way after you put down all the rocks.

Input

The first line contains only one integer T, which indicates the number of test cases.

For each test case, the first line contains N, M, L (0<=N<=2*10^5,1<=M<=10^9, 1<=L<=10^9).

And in the following N lines, each line contains one integer within (0, M) indicating the position of rock.

Output

For each test case, just output one line “Case #x: y", where x is the case number (starting from 1) and y is the maximal number of steps Matt should jump.

Sample Input