题解 | #DNA序列#

#include <iostream>
#include <string>
using namespace std;

float compute_GC_Ratio(string& str) {
    int n = str.size();
    float num = 0;
    for (int i = 0; i < n; i++) {
        if (str[i] == 'G' || str[i] == 'C') {
            num++;
        }
    }
    return num / n;
}

int main() {
    string geninp;
    int N;
    cin >> geninp >> N;
    int n = geninp.size();
    float maxgen = 0;
    string temp;
    string maxsubstr;
    for (int i = 0; i < n; i++) {
        for (int j = i + 1; j < n; j++) {
            if (j - i + 1 == N) {
                temp = geninp.substr(i, j - i + 1);
                float GC = compute_GC_Ratio(temp);
                if (maxgen < GC) {
                    maxsubstr = temp;
                    maxgen = GC;
                }
                break;
            }
        }
    }
    cout << maxsubstr;
}
// 64 位输出请用 printf("%lld")

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