题解 | DNA序列

#include <iostream>
#include <string>
using namespace std;
/*1.暴力解法
int main() {
    string s;
    cin>>s;
    int n,num=0,max=0,begin=0;
    cin>>n;
    int a, b;
    for(int i=0;i<s.size()-n+1;i++){
        for(int j=i;j<i+n;j++){
            if(s[j]=='G'||s[j]=='C')num++;
        }
        if(num>max){max=num;begin=i;}
        num=0;
    }
    for (auto it = begin; it <begin+n; it++) {
        cout << s[it];
    }
}
*/
//2.滑动窗口
//注意一点：循环的控制条件right<n,字符串最大下标为s[right],不要超过字符串范围
int main() {
    string s;
    int n = 0, left, right, resindex, count = 0, max = 0;
    while (cin >> s >> n) {
        for (auto i = 0; i < n; i++) {
            if (s[i] == 'G' || s[i] == 'C')count++;
        }
        max = count;
        resindex = 0;
        left = 1;
        right = n;
        if (s.size() > n) {
            while (right < s.size()) {
                if (s[left - 1] == 'G' || s[left - 1] == 'C')count--;
                if (s[right] == 'G' || s[right] == 'C')count++;
                if (count > max) {
                    max = count;
                    resindex = left;
                }
                left++;
                right++;
            }
        }
        cout << s.substr(resindex, n);
    }
}