UVA - 10881 Piotr's Ants

Piotr的蚂蚁问题：算法挑战

最新推荐文章于 2022-10-08 07:46:03 发布

原创最新推荐文章于 2022-10-08 07:46:03 发布 · 403 阅读

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这篇博客深入探讨了Piotr的蚂蚁问题，一个充满趣味的算法挑战。作者详细介绍了蚂蚁如何在水平杆上行走、碰撞及转向的机制，并通过实例展示了如何计算在特定时间后蚂蚁的位置和方向。此问题不仅考验了读者的空间想象能力，还涉及到算法设计与逻辑思维。文章最后提供了详细的代码解析，帮助读者理解并解决类似问题。

Piotr's Ants

Crawling in process...

Description

Problem D
Piotr's Ants
Time Limit: 2 seconds

"One thing is for certain: there is no stopping them;
the ants will soon be here. And I, for one, welcome our
new insect overlords."

Kent Brockman

Piotr likes playing with ants. He has n of them on a horizontal pole L cm long. Each ant is facing either left or right and walks at a constant speed of 1 cm/s. When two ants bump into each other, they both turn around (instantaneously) and start walking in opposite directions. Piotr knows where each of the ants starts and which direction it is facing and wants to calculate where the ants will end up T seconds from now.

Input
The first line of input gives the number of cases, N. N test cases follow. Each one starts with a line containing 3 integers: L , T and n (0 <= n <= 10000) . The next n lines give the locations of the n ants (measured in cm from the left end of the pole) and the direction they are facing (L or R).

Output
For each test case, output one line containing "Case #x:" followed by n lines describing the locations and directions of the n ants in the same format and order as in the input. If two or more ants are at the same location, print "Turning" instead of "L" or "R" for their direction. If an ant falls off the polebeforeT seconds, print "Fell off" for that ant. Print an empty line after each test case.

Sample Input	Sample Output
2 10 1 4 1 R 5 R 3 L 10 R 10 2 3 4 R 5 L 8 R	Case #1: 2 Turning 6 R 2 Turning Fell off Case #2: 3 L 6 R 10 R

Problemsetter: Igor Naverniouk
Alternate solutions: Frank Pok Man Chu and Yury Kholondyrev

Source

Root :: AOAPC I: Beginning Algorithm Contests -- Training Guide (Rujia Liu) :: Chapter 1. Algorithm Design :: General Problem Solving Techniques :: Examples
Root :: Prominent Problemsetters :: Igor Naverniouk (Abednego)

Problem descriptions:

System Crawler 2014-08-17

      Initialization.
      
     

大白书的机智题。代码：（详细解析见大白书）

#include <iostream>
#include<cstdio>
#include<algorithm>
#include<cmath>
using namespace std;
const int maxn=10000+10;
struct ANT
{
int pos,dir,id;//pos代表位置，dir代表方向（-1：左，0：转向中，1：右。设置成-1,0,1，是为位置等的计算方便），id代表输入顺序
bool operator <(const ANT &a)const
{
return pos<a.pos;
}
}before[maxn],after[maxn];
char dirt[][10]={"L","Turning","R"};
int order[maxn];//输入的第i只蚂蚁是终态左数的第order[i]只蚂蚁
int main()
{
int kase,l,t,n,i,j,k;
char c;
scanf("%d",&kase);
for(k=1;k<=kase;k++)
{
scanf("%d%d%d",&l,&t,&n);
for(i=0;i<n;i++)
{
scanf("%d %c",&before[i].pos,&c);//注意这里的%d %c之间有空格，否则c读入的是空格
after[i].dir=before[i].dir=c=='R'?1:-1;//把方向看成不变，相当于“穿行而过”
before[i].id=i;
after[i].pos=before[i].pos+t*before[i].dir;
}
sort(before,before+n);
for(i=0;i<n;i++)
{
order[before[i].id]=i;
}
sort(after,after+n);
printf("Case #%d:\n",k);
for(i=0;i<n-1;i++)
if(after[i].pos==after[i+1].pos)
after[i].dir=after[i+1].dir=0;
for(i=0;i<n;i++)
{
int m=order[i];
if(after[m].pos>l||after[m].pos<0)
printf("Fell off\n");
else
{
int num=after[m].dir;
printf("%d %s\n",after[m].pos,dirt[num+1]);
}
}
printf("\n");
}
return 0;
}

总结：

还是挺有趣的题目。

附录：

#include<bits/stdc++.h>包含C++的全部头文件

#include<bits/stdc++.h>包含C++的所有头文件

参考博客：http://blog.kuoe0.tw/posts/2014/01/31/install-gnu-gcc-on-os-x-and-use-the-header-bits-stdcplusplus-h-and-policy-based-data-structure

做CF看见别人用这个函数，然后就能直接用vector,set,string那些函数了，摸不着头脑，感觉特神奇就百度了一下，才发现这个是C++版本升级，然后文件自带的，方便了程序员吧。不然每次都得敲那模板老长……

使用和平常的头文件一样，如下：

#include<bits/stdc++.h>
using namespace std;
int main()
{
    int a,b;
    cin>>a>>b;
    cout<<a+b<<endl;
    return 0;
}

#include<bits/stdc++.h>这个头文件包含以下等等C++中包含的所有头文件：

#include <iostream>
#include <cstdio>
#include <fstream>
#include <algorithm>
#include <cmath>
#include <deque>
#include <vector>
#include <queue>
#include <string>
#include <cstring>
#include <map>
#include <stack>
#include <set>

等等……

不过在国内oj中，poj，hdu 不支持这个函数，这几个oj的编译器问题，其他国外的oj，还有台湾的oj都支持，CF，Topcoder也都支持。

所以把上面的题头文件全部删除，改成 #include<bits/stdc++.h>也AC了。