4.10华为第2题解答

import java.util.*;
public class HuaWeiQ5 {
public String expandString(String s) {
    boolean findNumber=false;
    for(int i=0;i<s.length();i++)
        if(Character.isDigit(s.charAt(i))) {
            findNumber=true;
            break;
        }
    if(!findNumber) {
        StringBuilder sb=new StringBuilder(s);
        sb.reverse();
        //return sb.toString();
        return s;
    }
    Stack<Character>stack=new Stack<Character>();
    int firstDigitPos=-1,lastDigitPos=-1;
        int i=0;
        while(!Character.isDigit(s.charAt(i)))i++;
        firstDigitPos=i;
        while(Character.isDigit(s.charAt(i)))i++;
        lastDigitPos=i-1;
        String part1=s.substring(0,firstDigitPos);
        String part2=s.substring(firstDigitPos,lastDigitPos+1);
        int leftParentesePos=lastDigitPos+1;
        int rightParentesePos=-1;
        //s[leftParentesePos]应该是一个括号,我们需要找到与它匹配的括号
        stack.push(s.charAt(leftParentesePos));
        for(i=leftParentesePos+1;i<s.length();i++) {
            if(isLeftParenthese(s.charAt(i)))
                    stack.push(s.charAt(i));
            else if(isRightParenthese(s.charAt(i)))
                stack.pop();
            if(stack.isEmpty()) {
                rightParentesePos=i;
                break;}
        }
        String part3=s.substring(leftParentesePos+1,rightParentesePos);
        String part4=s.substring(rightParentesePos+1);
        //System.out.println(part1);
        //System.out.println(part2);
        //System.out.println(part3);
        String later=expandString(part4);
                int repeatTimes=Integer.parseInt(part2);
        StringBuilder sb=new StringBuilder(part1);
        part3=expandString(part3);
        for(int j=0;j<repeatTimes;j++)
            sb.append(part3);
        sb.append(later);
    return sb.toString();
}
public boolean isLeftParenthese(char ch) {
    
    return ch=='('||ch=='['||ch=='{';
}
public boolean isRightParenthese(char ch) {
    
    return ch==')'||ch==']'||ch=='}';
}
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        //String s="abc3(A)";
        Scanner sc=new Scanner(System.in);
        String s=sc.nextLine();
        String ans=new HuaWeiQ5().expandString(s);
        System.out.println(ans);
    }
}