[LeetCode 题解]: 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.
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 n^th sequence.

Note: The sequence of integers will be represented as a string.

本题的难点在于理解题目的意思。

最好的理解就是给出 111221之后的一个sample： 312211

如何理解呢？将111221 拆成后面的表达式即可： 111， 22， 1 其中有 3个one ， 2个two， 1个one ，读起来就是： 312211

 1 class Solution {
 2 public:
 3     string countAndSay(int n) {
 4         string a="1";
 5         if(n==1) return a;
 6         for(int i=2;i<=n;i++)
 7         {
 8             string b;
 9             char current = a[0];
10             int j=1,count=1;
11             for(j=1;j<a.size();j++)
12             {
13                 if(a[j]==current)
14                 {
15                     count++;
16                 }
17                 else
18                 {
19                     char c = count +'0';
20                     b+=c;
21                     b+=current;
22                     current = a[j];
23                     count=1;
24                 }
25             }
26             char c = count+'0';
27             b+=c;
28             b+=current;
29             a= b;
30         }
31         return a;
32     }
33 };

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