LeetCode38. Count and Say
Posted 华仔要长胖
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Difficulty:easy
More:【目录】LeetCode Java实现
Description
https://leetcode.com/problems/count-and-say/
The count-and-say sequence is the sequence of integers with the first five terms as following:
1. 1 2. 11 3. 21 4. 1211 5. 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 where 1 ≤ n ≤ 30, generate the nth term of the count-and-say sequence.
Note: Each term of the sequence of integers will be represented as a string.
Example 1:
Input: 1 Output: "1"
Example 2:
Input: 4 Output: "1211"
Intuition
Straightforward
Solution
public String countAndSay(int n) { String str="1"; if(n==1) return str; while(n>1){ str=getNext(str); n--; } return str; } private String getNext(String str){ StringBuilder sb = new StringBuilder(); int i=0; while(i<str.length()){ char num=str.charAt(i); int count=0; while(i<str.length() && str.charAt(i)==num){ i++; count++; } sb.append(count).append(num); } return sb.toString(); }
Complexity
What I\'ve learned
More:【目录】LeetCode Java实现
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