2025.2.17——1400

合集 - 日常训练(56)

1.2025.2.19——150002-192.11.23 周六2024-11-243.11.24 周日2024-11-254.11.25 周一日常2024-11-265.2024.11.26 周二日常2024-11-266.2024.11.27 周三2024-11-277.2024.11.28周四2024-11-288.2024.11.29 周五2024-11-299.2024.11.30 周六2024-11-3010.2024.12.1 周日2024-12-0211.2024.12.2 周一2024-12-0212.2024.12.3 周二2024-12-0413.2024.12.4 周三2024-12-0514.2024.12.5 周四2024-12-0615.2024.12.7 周六2024-12-0816.2024.12.8 周日2024-12-0917.2024.12.9 周一2024-12-1018.2024.12.10 周二2024-12-1119.2024.12.11 周三2024-12-1220.2024.12.12 周四2024-12-1321.2024.12.13 周五2024-12-1422.2024.12.14 周六2024-12-1523.2024.12.16 周一2024-12-1724.2024.12.17 周二2024-12-1825.2024.12.18 周三2024-12-1926.2024.12.19 周四2024-12-2027.2024.12.20 周五2024-12-2128.2024.12.21 周六2024-12-2229.2024.12.22 周日2024-12-2330.2024.12.23 周一2024-12-2431.2024.12.24 周四2024-12-2532.2024.12.25 周三2024-12-2633.2024.12.26 周四2024-12-2834.2024.12.27 周五2024-12-2835.2024.12.28 周六2024-12-2936.2024.12.29 周日2024-12-3037.2024.12.30 周一01-0138.2025.1.5——120001-1439.2025.1.12——120001-1440.2025.1.14——120001-1541.2025.1.15——120001-1642.2025.1.16——120001-1743.2025.1.17——120001-1844.2025.1.18——130001-1945.2025.1.19——130001-2046.2025.1.20——130001-2147.2025.1.21——130001-2248.2025.1.22——130001-2449.2025.1.24——140001-2650.2025.1.26——140001-2851.2025.2.8——140002-0952.2025.2.9——140002-1153.2025.2.10——140002-1154.2025.2.14——140002-1455.2025.2.15——140002-15

56.2025.2.17——140002-17

收起

2025.2.17——1400

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A 1400

B 1400

C 1400

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• 二分+构造+字符串/贪心/思维。CF的题就得多看透几层表面发掘本质。

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A

1. 一眼单调性。
2. 分析后可以二分答案。

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B

1. 本质是：$(j-i)|n,s[i]!=s[j]$ 。设想一个周期为 $T$ 。
2. 设最小的不能被 $n$ 整除的数为 $t$ 。必要性：$T>=t$ 。充分性：$T==t$ 时，$s[i]==s[j]$的距离为 $t$ 的倍数，不能被 $n$ 整除，满足题意。
3. 绝妙的构造..

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C

1. 字符串贪心匹配。看着题解想了好久，值得多几次回味。解法和优化亦多样，正难则反/搜索/动态规划..

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------------------------代码------------------------

A

#include <bits/stdc++.h>
#define int long long
using namespace std;
#define bug(BUG) cout << "bug:# " << (BUG) << endl
#define bug2(BUG1, BUG2) cout << "bug:# " << (BUG1) << " " << (BUG2) << endl
#define bug3(BUG1, BUG2, BUG3) cout << "bug:# " << (BUG1) << ' ' << (BUG2) << ' ' << (BUG3) << endl
#define bugv(VEC)               \
    {                           \
        for (auto Vec : VEC)    \
            cout << Vec << ' '; \
        cout << '\n';           \
    }

void _();
signed main()
{
    ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    cout << fixed << setprecision(10);
    int T = 1;
    cin >> T;
    while (T--)
        _();
    return 0;
}

void _()
{
    int n;
    cin >> n;
    vector<int> a(n + 1);
    for (int i = 1; i <= n; i++)
        cin >> a[i];
    sort(begin(a) + 1, end(a));
    // bugv(a);

    auto ok = [&](int x)
    {
        int cnt = 0;
        // bug2(1, x);
        for (int i = 1; i <= n;)
        {
            int j = i;
            cnt++;
            for (; j <= n && a[j] - a[i] <= x << 1; j++)
                ;
            i = j;
            // bug(i);
        }
        // bug2(2, cnt);
        return cnt <= 3;
    };
    // ok(2);
    int l = -1, r = 1e9;
    while (r - l - 1)
    {
        int mid = l + r >> 1;
        if (ok(mid))
            r = mid;
        else
            l = mid;
    }
    cout << r << '\n';
}

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B

#include <bits/stdc++.h>
#define int long long
using namespace std;
#define bug(BUG) cout << "bug:# " << (BUG) << endl
#define bug2(BUG1, BUG2) cout << "bug:# " << (BUG1) << " " << (BUG2) << endl
#define bug3(BUG1, BUG2, BUG3) cout << "bug:# " << (BUG1) << ' ' << (BUG2) << ' ' << (BUG3) << endl
#define bugv(VEC)               \
    {                           \
        for (auto Vec : VEC)    \
            cout << Vec << ' '; \
        cout << '\n';           \
    }

void _();
signed main()
{
    ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    cout << fixed << setprecision(10);
    int T = 1;
    cin >> T;
    while (T--)
        _();
    return 0;
}

void _()
{
    int n;
    cin >> n;
    int st = 1;
    while (n % st == 0)
        st++;
    for (int i = 0; i < n; i++)
        cout << (char)('a' + i % st);
    cout << '\n';
}

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C

#include <bits/stdc++.h>
#define int long long
using namespace std;
#define bug(BUG) cout << "bug:# " << (BUG) << endl
#define bug2(BUG1, BUG2) cout << "bug:# " << (BUG1) << " " << (BUG2) << endl
#define bug3(BUG1, BUG2, BUG3) cout << "bug:# " << (BUG1) << ' ' << (BUG2) << ' ' << (BUG3) << endl
#define bugv(VEC)               \
    {                           \
        for (auto Vec : VEC)    \
            cout << Vec << ' '; \
        cout << '\n';           \
    }

void _();
signed main()
{
    ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    cout << fixed << setprecision(10);
    int T = 1;
    cin >> T;
    while (T--)
        _();
    return 0;
}

void _()
{
    string s;
    cin >> s;
    int m;
    cin >> m;
    string l, r;
    cin >> l >> r;
    int st = 0;
    int n = s.size();
    s = ' ' + s;
    for (int i = 0; i < m; i++)
    {
        int mx = st + 1;
        for (int j = l[i] - '0'; j <= r[i] - '0'; j++)
        {
            int t = st + 1;
            while (t <= n && j != s[t] - '0')
                t++;
            mx = max(mx, t);
        }
        st = mx;
    }
    cout << (st > n ? "YES" : "NO") << '\n';
}

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