POJ3617 Best Cow Line

文章链接：http://poj.org/problem?id=3617

Best Cow Line

Time Limit: 1000MS Memory Limit: 65536KTotal Submissions: 20242 Accepted: 5568

Description

FJ is about to take his N (1 ≤ N ≤ 2,000) cows to the annual"Farmer of the Year" competition. In this contest every farmer arranges his cows in a line and herds them past the judges.

The contest organizers adopted a new registration scheme this year: simply register the initial letter of every cow in the order they will appear (i.e., If FJ takes Bessie, Sylvia, and Dora in that order he just registers BSD). After the registration phase ends, every group is judged in increasing lexicographic order according to the string of the initials of the cows' names.

FJ is very busy this year and has to hurry back to his farm, so he wants to be judged as early as possible. He decides to rearrange his cows, who have already lined up, before registering them.

FJ marks a location for a new line of the competing cows. He then proceeds to marshal the cows from the old line to the new one by repeatedly sending either the first or last cow in the (remainder of the) original line to the end of the new line. When he's finished, FJ takes his cows for registration in this new order.

Given the initial order of his cows, determine the least lexicographic string of initials he can make this way.

Input

* Line 1: A single integer: N
* Lines 2..N+1: Line i+1 contains a single initial ('A'..'Z') of the cow in the ith position in the original line

Output

The least lexicographic string he can make. Every line (except perhaps the last one) contains the initials of 80 cows ('A'..'Z') in the new line.

Sample Input

6ACDBCB

Sample Output

ABCBCD

Source

USACO 2007 November Silver

这是一道贪心的题，根据给的字符串，每次从字符串的“头部”或“尾部”拿掉一个组成一个新的字符串，是这个新组成的字符串的字典序尽可能的小，      所以，每次选择字典序小的字符来添加到新字符串里边，如果头部和尾部的字典序一样，那就比下一位，直到不相同为止

代码如下：

#include <iostream>#include <cstdio>#include <cstring>using namespace std;int main(){    int n;    while(~scanf("%d",&n))    {        string s;        for(int i=0;i<n;i++)        {            getchar();            char temp;            scanf("%c",&temp);            s += temp;        }        int len = s.length() - 1;        int Count = 0;        int lengthCount = 0;        while(Count<=len)        {            bool left = false;            for(int i=0;Count+i<=len;i++)            {                if(s[Count+i]<s[len-i])                {                    left = true;                    break;                }                else if(s[Count+i]>s[len-i])                {                    left = false;                    break;                }            }            if(left) printf("%c",s[Count++]);            else printf("%c",s[len--]);            lengthCount++;            lengthCount%=80;            if(lengthCount%80==0) printf("\n");        }        if(s.length()%80) printf("\n");    }    return 0;}