题解 | DNA序列

#include <iostream>
using namespace std;

int main() 
{
    string str;
    int n;
    cin >> str >> n;

    int left = 0, right = 0;
    int begin = 0, count = 0, max_sum = 0;
    while(right < str.size())
    {
        if(str[right] == 'C' || str[right] == 'G') count++;
        if(right - left + 1 == n)
        {
            if(max_sum < count) 
            {
                max_sum = count;
                begin = left;
            }
            if(str[left] == 'C' || str[left] == 'G') count--;
            left++;
        }
        right++;
    }    
    cout << str.substr(begin, n) << endl;
    return 0;
}