Leetcode 38.Count and Say (counting and speaking) ideas and methods for solving problems

Source: Internet
Author: User

Count and Say

The Count-and-say sequence is the sequence of integers beginning as follows:
1, 11, 21, 1211, 111221, ...

1 is read off as "one 1" or 11.
One is read off as "1s" or 21.
is read off as "One 2, then one 1" or 1211.
Given an integer n, generate the nth sequence.

Note:the sequence of integers would be represented as a string.

Idea: Test instructions is really too difficult to understand, especially English is not good, can only see someone else's information, understand the rules. Finally understand, test instructions is n=1 when the output string 1;n=2, the number of the last string, because the last string has a 1, so the output 11;n=3, because the last character is 11, there are 2 1, so the output 21;n=4, because the last string is 21, There is a 2 and a 1, so the output is 1211. Write a Countandsay (n) function to return the string, in turn.

Test instructions Understanding after the good run, is a typical recursive problem, the code is very simple, as follows:

public class Solution {public    String countandsay (int n) {        if (n = = 1) {            return "1";        }        A recursive call is then processed on string        str = Countandsay (n-1) + "*";//For the mark at the end of STR, convenient for loop reading        char[] C = Str.tochararray ();        int count = 1;        String s = "";        for (int i = 0; i < c.length-1;i++) {        if (c[i] = = C[i+1]) {        count++;//count increased        }else{        s = s + count + c[i ];//the * mark above is convenient for unified processing        count = 1;//initialization        }        }        return s;    }

Copyright NOTICE: This article for Bo Master original article, without Bo Master permission not reproduced.

Leetcode 38.Count and Say (counting and speaking) ideas and methods for solving problems

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