把已匹配到的方括号换成花括号，最后再换回来

把已匹配到的方括号换成花括号，最后再换回来：

import java.util.*;
public class Main{
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        StringBuilder r = new StringBuilder(sc.nextLine());
        while(r.indexOf("]") != -1){
            int j = r.indexOf("]");
            r.setCharAt(j, '}');
            int i = j - 1;
            while(i >= 0 && r.charAt(i) != '[') i--;
            if(i < 0) r.insert(0, '{');
            else r.setCharAt(i, '{');
        }
        int c = 0;
        for(int i = 0; i < r.length(); ++i){
            if(r.charAt(i) == '[') c++;
        }
        for(int i = 0; i < r.length(); ++i){
            if(r.charAt(i) == '{') r.setCharAt(i, '[');
            if(r.charAt(i) == '}') r.setCharAt(i, ']');
        }
        while(c-- > 0) r.append("]");
        System.out.println(r);
    }
}