LeetCode 38. Count and Say

https://leetcode.com/problems/count-and-say/description/

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, 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"

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Hide Hint 1  

The following are the terms from n=1 to n=10 of the count-and-say sequence:

 1.     1
 2.     11
 3.     21
 4.     1211
 5.     111221 
 6.     312211
 7.     13112221
 8.     1113213211
 9.     31131211131221
10.     13211311123113112211

Hide Hint 2   

To generate the  nth term, just  count and say the  n-1th term.

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• 字符串簡單題。主要是分析清楚模擬算法。
• to_string - C++ Reference
  • http://www.cplusplus.com/reference/string/to_string/

 1 //
 2 //  main.cpp
 3 //  LeetCode
 4 //
 5 //  Created by Hao on 2017/3/16.
 6 //  Copyright © 2017年 Hao. All rights reserved.
 7 //
 8 
 9 #include <iostream>
10 #include <cstring>
11 #include <vector>
12 using namespace std;
13 
14 class Solution {
15 public:
16     string countAndSay(int n) {
17         if (n <= 0) return ""; // corner case
18         
19         string sResult = "1", sTemp = "";
20         int count = 0, j = 0;
21         
22         for (int i = 1; i < n; i ++) {
23             j = 0;
24             sTemp = "";
25             
26             while (j < sResult.size()) {
27                 count = 1;
28                 
29                 while (j + 1 < sResult.size() && sResult.at(j) == sResult.at(j + 1)) {
30                     ++ j;
31                     ++ count;
32                 }
33                 
34                 sTemp = sTemp + to_string(count) + sResult.at(j);
35                 
36                 ++ j;
37             }
38             
39             sResult = sTemp;
40         }
41         
42         return sResult;
43     }
44 };
45 
46 int main(int argc, char* argv[])
47 {
48     Solution    testSolution;
49     string      result;
50     
51     vector<int> iVec = {0, 1, 2, 3, 4, 5};
52     
53     /*
54      
55      1
56      11
57      21
58      1211
59      111221
60      */
61     for (auto i : iVec) {
62         cout << testSolution.countAndSay(i) << endl;
63     }
64 
65     return 0;
66 }

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