Careercup - Google面试题 - 6253551042953216

2014-05-06 01:49

题目链接

原题：

Modify the following code to add a row number for each line is printed







public class Test {

    public static void main(String [] args){

        printParenthesis(3);

    }

    public static void printParenthesis(int n){

        char buffer[] = new char[n*2];

        printP(buffer,0,n,0,0);

    }

    public static void printP(char buffer[], int index, int n, int open, int close){

        if(close == n){

            System.out.println(new String(buffer));

        }else{

            if(open > close){

                buffer[index] = ']';

                printP(buffer, index+1, n, open, close+1);

            }

            if(open < n ){

                buffer[index] = '[';

                printP(buffer,index+1,n,open+1,close);

            }

        }

    }

}



Expected Output:







1.[][][]

2.[][[]]

3.[[]][]

4.[[][]]

5.[[[]]]



What changes needs to be done to accomplish the output expected?

题目：给下面的代码加上一些修改，使得输出的结果能带有序号，如示例中的格式。

解法：代码可能还不太明显，但从结果一看就知道是输出N对括号匹配的所有组合，并且卡塔兰数H(3) = 5，也符合条件。只要加上一个全局的counter，并且在输出语句附近给counter加1，就可以带序号输出了。

代码：

 1 // http://www.careercup.com/question?id=6253551042953216

 2 public class Test {

 3     static int res_count = 0;

 4     

 5     public static void main(String [] args) {

 6         printParenthesis(3);

 7     }

 8     

 9     public static void printParenthesis(int n) {

10         char buffer[] = new char[n * 2];

11         res_count = 0;

12         printP(buffer, 0, n, 0, 0);

13     }

14     

15     public static void printP(char buffer[], int index, int n, int open, int close) {

16         if(close == n) {

17             System.out.print((++res_count) + ".");

18             System.out.println(new String(buffer));

19         } else {

20             if (open > close) {

21                 buffer[index] = ']';

22                 printP(buffer, index+1, n, open, close + 1);

23             }

24             if (open < n) {

25                 buffer[index] = '[';

26                 printP(buffer, index + 1, n, open + 1, close);

27             }

28         }

29     }

30 }