Count Binary Substrings问题及解法

问题描述：

Give a string 

s

, count the number of non-empty (contiguous) substrings that have the same
number of 0's and 1's, and all the 0's and all the 1's in these substrings are grouped consecutively.

Substrings that occur multiple times are counted the number of times they occur.

示例:

Input: "00110011"
Output: 6
Explanation: There are 6 substrings that have equal number of consecutive 1's and 0's: "0011", "01", "1100", "10", "0011", and "01".

Notice that some of these substrings repeat and are counted the number of times they occur.

Also, "00110011" is not a valid substring because all the 0's (and 1's) are not grouped together.

Input: "10101"
Output: 4
Explanation: There are 4 substrings: "10", "01", "10", "01" that have equal number of consecutive 1's and 0's.

问题分析：

统计相邻的0和1的个数，每个0和1个数之间，取其最小值，取得的这个最小值之和加起来即为答案。

过程详见代码：

class Solution {
public:
int countBinarySubstrings(string s) {
int res = 0;
vector<int> vs;
char last = s[0];
int count = 1;
for (int i = 1; i < s.length();i++)
{
if (s[i] == s[i - 1]) count++;
else
{
vs.emplace_back(count);
count = 1;
}
}
vs.emplace_back(count);
for (int i = 1; i < vs.size(); i++)
{
res += min(vs[i], vs[i - 1]);
}
return res;
}
};