Codeforces Round #690 (Div. 3)

1462A. Favorite Sequence

簡單看懂題即可，左邊輸出一個然後右邊輸出一個。

void solve() {
    int n;
    cin >> n;
    vector<ll> a(n + 1);
    // ll a[n + 1]; //兩種寫法均可
    for (int i = 1; i <= n; ++i)
        cin >> a[i];
    int l = 1, r = n;
    bool f = true;
    for (int i = 1; i <= n; ++i) {
        if (f)
            cout << a[l++] << " ", f = false;
        else
            cout << a[r--] << " ", f = true;
    }
    cout << endl;
}
 

1462B. Last Year's Substring

一開始想錯了，正確的思路是拆分字串看是否能組成 2020

void solve() {
    int n;
    string s;
    cin >> n >> s;
    bool f = false;

    for (int fir = 0; fir <= 4 && !f; fir++) {
        int sec = 4 - fir;  //定位

        if (s.substr(0, fir) + s.substr(n - sec) == "2020")
            f = true;
    }

    cout << (f ? "YES\n" : "NO\n");
}
 

1462C. Unique Number