PTA 倒数第N个字符串 Java

PTA 倒数第N个字符串 Java

题目相当于是做进制转换，‘z’表示0，‘a’表示25
则将十进制数N转换成26进制（‘z’~‘a’)，不足L位用’z’（0）填充

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.StringTokenizer;

public class Main {
	public static void main(String[] args) throws IOException {
		Reader.init(System.in);
		Writer.init(System.out);
		slove();
		Writer.close();
	}

	// 解答入口
	static void slove() throws IOException {
		int l = Reader.nextInt();
		// 转化成26进制进行计算，'a' = 25 ，'z' = 0
		// 字符使用ASCII 进行换算 
		// 'a' = 25- 25 + 'a' 'z' = 25 - 0 + 'z'
		// 因为倒数第一个是'zzz'就是'000'
		// 即求倒数第1个数字是值为'0‘的时候
		int n = Reader.nextInt() - 1;
		// 这里使用StringBuilder 为了后面倒序输出
		StringBuilder s = new StringBuilder();
		while (n > 0) {
			int tmp = n % 26;
			s.append((char) (25 - tmp + 'a'));
			n /= 26;
		}
		// 补上前导0,即'z'
		int add = l - s.length();
		for (int i = 0; i < add; i++) {
			s.append('z');
		}
		// 倒过来输出
		Writer.print(s.reverse());
		
	}

}

class School {
	ArrayList<String> ids;
	int capacity;

	School(int capacity) {
		this.capacity = capacity;
		ids = new ArrayList<String>(capacity);
	}
}

// 以下是输入输出模板和思路逻辑无关
class Reader {
	static BufferedReader reader;
	static StringTokenizer tokenizer;

	// ** call this method to initialize reader for InputStream *//*
	static void init(InputStream input) {
		reader = new BufferedReader(new InputStreamReader(input));
		tokenizer = new StringTokenizer("");
	}

	// ** get next word *//*
	static String next() throws IOException {
		while (!tokenizer.hasMoreTokens()) {
			tokenizer = new StringTokenizer(reader.readLine());
		}
		return tokenizer.nextToken();
	}

	static String nextLine() throws IOException {
		return reader.readLine();
	}

	static int nextInt() throws IOException {
		return Integer.parseInt(next());
	}

	static long nextLong() throws IOException {
		return Long.parseLong(next());
	}

	static char nextChar() throws IOException {
		return next().toCharArray()[0];
	}

	static float nextFloat() throws IOException {
		return Float.parseFloat(next());
	}

	static Double nextDouble() throws IOException {
		return Double.parseDouble(next());
	}
}

class Writer {
	static BufferedWriter writer;

	static void init(OutputStream outputStream) {
		writer = new BufferedWriter(new OutputStreamWriter(outputStream));
	}

	static void print(Object object) throws IOException {
		writer.write(object.toString());
	}

	static void println(Object object) throws IOException {
		writer.write(object.toString());
		writer.write("\n");
	}

	static void close() throws IOException {
		// TODO Auto-generated method stub
		writer.close();
	}
}