Codeforces Round 871 (Div. 4) ABCDEF

很久没写题目了，划点水题

A. Love Story

#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
typedef pair<LL, LL> PII;
const LL MAXN = 1e18;
const LL N = 1e6, M = 4002;
const LL mod = 1e9 + 7; 
int main()
{
    //cin.tie(0); cout.tie(0); ios::sync_with_stdio(false);
    LL T = 1;
    cin>>T;
    while (T--)
    {
        string s = "codeforces";
        string c;
        cin >> c;
        LL ans = 0;
        for (int i = 0; i < c.size(); i++)
        {
            if (s[i] != c[i]) ans++;
        }
        cout << ans << endl;
    }
    return 0;
}

B. Blank Space

#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
typedef pair<LL, LL> PII;
const LL MAXN = 1e18;
const LL N = 1e6, M = 4002;
const LL mod = 1e9 + 7; 
LL a[N];
int main()
{
    cin.tie(0); cout.tie(0); ios::sync_with_stdio(false);
    LL T = 1;
    cin>>T;
    while (T--)
    {
        LL n;
        cin >> n;
        for (int i = 1; i <= n; i++)
        {
            cin >> a[i];
        }
        LL flag = 0;
        LL maxn = 0;
        for (int i = 1; i <= n; i++)
        {
            if (a[i] == 1) flag = 0;
            else flag++;
            maxn = max(maxn, flag);
        }
        cout << maxn << endl;
    }
    return 0;
}

C. Mr. Perfectly Fine

#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
typedef pair<LL, LL> PII;
const LL MAXN = 1e18;
const LL N = 1e6, M = 4002;
const LL mod = 1e9 + 7; 
LL a[N];
int main()
{
    cin.tie(0); cout.tie(0); ios::sync_with_stdio(false);
    LL T = 1;
    cin>>T;
    while (T--)
    {
        LL n;
        cin >> n;
        LL minn = MAXN;
        LL ly = MAXN, yl = MAXN;
        for (int i = 1; i <= n; i++)
        {
            LL x, y;
            cin >> x >> y;
            if (y == 11) minn = min(minn, x);
            else if (y == 01) ly = min(ly, x);
            else if (y == 10) yl = min(yl, x);
        }
        minn = min(minn, ly + yl);
        if (minn >= MAXN / 2) minn = -1;
        cout << minn << endl;
    }
    return 0;
}

D. Gold Rush

#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
typedef pair<LL, LL> PII;
const LL MAXN = 1e18;
const LL N = 1e6, M = 4002;
const LL mod = 1e9 + 7; 
LL a[N];
bool check(LL n, LL m)
{
    queue<LL> q;
    if (n / 3 == m || n / 3 * 2 == m) return true;
    if(n/3>=m)  q.push(n / 3);
    if(n/3*2>=m) q.push(n / 3 * 2);
    while (q.size())
    {
        auto t = q.front();
        q.pop();
        if (t % 3 == 0)
        {
            if (t / 3 == m || t / 3 * 2 == m) return true;
            if (t / 3 >= m)  q.push(t / 3);
            if (t / 3 * 2 >= m) q.push(t / 3 * 2);
        }
    }
    return false;
}
int main()
{
    //cin.tie(0); cout.tie(0); ios::sync_with_stdio(false);
    LL T = 1;
    cin>>T;
    while (T--)
    {
        LL n, m;
        cin >> n >> m;
        if (n == m) cout << "YES" << endl;
        else if (n < m) cout << "NO" << endl;
        else if (n % 3 != 0) cout << "NO" << endl;
        else {
            if (check(n, m) == true) cout << "YES" << endl;
            else cout << "NO" << endl;
        }
    }
    return 0;
}

E. The Lakes

#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
typedef pair<LL, LL> PII;
const LL MAXN = 1e18;
const LL N = 1e6, M = 4002;
const LL mod = 1e9 + 7; 
LL a[M][M];
bool st[M][M];
LL n, m;
LL dx[] = { -1,0,0,1 }, dy[] = { 0,1,-1,0 };
LL sum = 0, maxn = 0;
void dfs(int x, int y)
{
    st[x][y] = true;
    sum += a[x][y];
    for (int i = 0; i < 4; i++)
    {
        LL xx = dx[i] + x, yy = dy[i] + y;
        if (xx >= 1 && xx <= n && yy >= 1 && yy <= m && st[xx][yy] == false && a[xx][yy] != 0)
        {
            dfs(xx, yy);
        }
    }
}
int main()
{
    cin.tie(0); cout.tie(0); ios::sync_with_stdio(false);
    LL T = 1;
    cin>>T;
    while (T--)
    {
        cin >> n >> m;
        for (int i = 1; i <= n; i++)
        {
            for (int j = 1; j <= m; j++)
            {
                cin >> a[i][j];
                st[i][j] = false;
            }
        }
        sum = 0;
        maxn = 0;
        for (int i = 1; i <= n; i++)
        {
            for (int j = 1; j <= m; j++)
            {
                if (st[i][j] == false&&a[i][j]!=0)
                {
                    sum = 0;
                    dfs(i, j);
                    maxn = max(maxn, sum);
                }
            }
        }
        cout << maxn << endl;
    }
    return 0;
}

F. Forever Winter

#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
typedef pair<LL, LL> PII;
const LL MAXN = 1e18;
const LL N = 1e6, M = 4002;
const LL mod = 1e9 + 7; 
LL n, m;
LL a[N], b[N];
LL d[N], deep[N];
LL maxn = 0;
vector<LL> g[N];
void init()
{
    maxn = 0;
    memset(deep, 0, sizeof deep);
    memset(d, 0, sizeof d);
    for (int i = 0; i <= 1000; i++)
    {
        g[i].clear();
    }
}
void dfs(LL idx, LL depth,LL father)
{
    maxn = max(maxn, depth);
    LL sum = g[idx].size();
    deep[depth]=max(deep[depth],sum);
    for (int i = 0; i < g[idx].size(); i++)
    {
        if (g[idx][i] == father) continue;
        dfs(g[idx][i], depth + 1, idx);
    }
}  
int main()
{
    cin.tie(0); cout.tie(0); ios::sync_with_stdio(false);
    LL T = 1;
    cin>>T;
    while (T--)
    {
        cin >> n >> m; 
        init();
        for (int i = 1; i <= m; i++)
        {
            cin >> a[i] >> b[i];
            g[a[i]].push_back(b[i]);
            d[a[i]]++;
            g[b[i]].push_back(a[i]);
            d[b[i]]++;
        }
        LL beg = 0;
        for (int i = 1; i <= m; i++)
        {
            if (d[a[i]] == 1)
            {
                beg = a[i];
                break;
            }
            else if(d[b[i]]==1)
            {
                beg = b[i];
                break;
            }
        }
        dfs(beg, 1,-1); 
        cout << deep[maxn / 2 + 1] << " " << deep[maxn - 1]-1 << endl;
    }
    return 0;
}