POJ3617 Best Cow Line

来源：互联网发布：网络是一把双刃剑编辑：程序博客网时间：2024/06/01 09:00

题意：给出一个字符串s，每次从字符串s首部或者尾部取一个字符，拼成新的字符，使得字典序最小。

思路：使用贪心算法。

（1）如果首部字符小于尾部字符，取首部字符

（2）如果首部字符大于尾部字符，取尾部字符

（3）如果首部字符等于尾部字符，取首部或者尾部都可以

代码如下：

import java.io.*;import java.util.Scanner;class Solution{    public static String solve(String s)    {        int start = 0, end = s.length() - 1;        StringBuilder sb = new StringBuilder();        while (start <= end)        {            boolean left = false;            for (int i = 0; i + start <= end; i++)            {                if (s.charAt(start + i) < s.charAt(end - i))                {                    left = true;                    break;                }                else if (s.charAt(start + i) > s.charAt(end - i))                {                    left = false;                    break;                }            }            if (left)            {                sb.append(s.charAt(start++));            }            else            {                sb.append(s.charAt(end--));            }        }        return sb.toString();    }}class MySystem{    private static Scanner cin;    private static PrintWriter cout;    private final static boolean DEBUG = false;    private MySystem(){}    static {        init();    }    private static void init()    {        try {            if (DEBUG) {                cin = new Scanner(new BufferedInputStream(new FileInputStream("d:\\program\\intelj\\spoj\\src\\spoj.txt")));            }            else            {                cin = new Scanner(new BufferedInputStream(System.in));            }            cout = new PrintWriter(new BufferedOutputStream(System.out));        }        catch (IOException e)        {            e.printStackTrace();        }    }    public static Scanner getInput()    {        return cin;    }    public static PrintWriter getOutput()    {        return cout;    }}public class Main {    public static void main(String[] args)    {        Scanner cin = MySystem.getInput();        PrintWriter cout = MySystem.getOutput();        while (cin.hasNext())        {            int n = cin.nextInt();            StringBuilder sb = new StringBuilder();            for (int i = 0; i < n; i++)            {                sb.append(cin.next());            }            String ans = Solution.solve(sb.toString());            int limit = 80;            int lines = (ans.length() + limit - 1)/ limit;            for (int i = 0; i < lines; i++)            {                if (i != lines - 1) cout.println(ans.substring(i * limit, (i + 1) * limit));                else cout.print(ans.substring(i * limit));            }            cout.flush();        }    }}

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