CSP认证2020-06-4-1246-(Java)32分

1246

问题描述
试题编号： 202006-4
试题名称： 1246
时间限制： 1.0s
内存限制： 512.0MB


Java语言32分
测试9–25，n的值太大，运行时间不过关。(水平实在低，拿一分算一分)

Java代码如下

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {
    public static void main(String [] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        String str_n = br.readLine();
        int n = Integer.valueOf(str_n);
        StringBuilder s_orig = new StringBuilder("1");
        String s_sub = br.readLine();

        for(int i = 1;i <= n;i++){
            int s_length = s_orig.length();
            int index = 0;
            for(int j = 0;j < s_length;j++,index++){
                switch(s_orig.charAt(index)){
                    case '1':
                        s_orig.replace(index, (index+1), "2");
                        break;
                    case '2':
                        s_orig.replace(index, (index+1), "4");
                        break;
                    case '4':
                        s_orig.replace(index, (index+1), "16");
                        index++;     // 一位变两位，索引再加一
                        break;
                    case '6':
                        s_orig.replace(index, (index+1), "64");
                        index++;
                        break;
                }
            }
        }

        String res = s_orig.toString();
        int res_length = res.length();
        int sub_length = s_sub.length();
        long count = 0;
        for(int i = 0;i <= res_length-sub_length;i++){
            if(res.charAt(i) == s_sub.charAt(0) && res.substring(i, i+sub_length).equals(s_sub)){
                count++;
                count %= 998244353;
            }
        }
        System.out.println(count);
    }
}

若有好方法，欢迎评论！