POJ - 3617 Best Cow Line(水+贪心)

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Best Cow Line

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 23288		Accepted: 6334

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

6
A
C
D
B
C
B

Sample Output

ABCBCD

题目大意：一个长度为N的字符串，可以从字符串头部删除一个元素，也可以从字符串尾部删除一个元素，加到一个新的字符空串的尾部，使得新的字符串字典序最小。

只需要每次判断字符串头部是否小于尾部然后决定删除哪一个元素即可，然后对于头尾相同的，不断循环比较下一个字符。

附上AC代码：

#include

using namespace std;
const int maxn=2000+5;
int n;
char c[maxn];

int main()
{
    cin>>n;
    for(int i=0;i>c[i];
    int l=0,r=n-1;

    while(l<=r)
    {
        bool left=false;
        for(int i=0;i+lc[r-i])
            {
                left=false;
                break;
            }
        }
        if(left)putchar(c[l++]);
            else putchar(c[r--]);
    }
    cout<