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
.
11
is read off as "two 1s"
or 21
.
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 will be represented as a string.
解题思路:
题目的理解很关键,n=1时返回“1”,n=2时返回“11”,n=3时返回"21",n=4时返回"1211"
所以肯定是用递归也进行求解,JAVA实现如下:
static public String countAndSay(int n) { if(n==1) return "1"; return countAndSay(countAndSay(n-1)); } static String countAndSay(String s){ StringBuilder sb = new StringBuilder(); int count = 0; char temp='*'; for(int i=0;i<s.length();i++){ if(temp!=s.charAt(i)){ if(temp!='*'){ sb.append(count); sb.append(temp); } count=1; temp=s.charAt(i); } else count++; } sb.append(count); sb.append(temp); return sb.toString(); }