[算法导论] 字符串变换

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;
 class Main {
    public static void main(String[] args) throws Exception{
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        String line = br.readLine();
        List<String> r = new ArrayList<>();
        r.add(" ");
        while(line!=null){
            r.add(line);
            line = br.readLine();
        }
        String originStr = r.get(0);
        for(int idx=1; idx < r.size(); idx+=2){
            String src = r.get(idx);
            String dst = r.get