Acwing杯第18周周赛

AcWing 3988. 不同的数

#include <iostream>
#include <cstring>
#include <algorithm>
#include <unordered_map>

using namespace std;

const int N = 110;
unordered_map<int, int> mp;

int main()
{
    int n, k;
    cin >> n >> k;
    
    for (int i = 1; i <= n; i ++ )
    {
        int x;
        cin >> x;

        mp[x] = i;
    }
    
    if (mp.size() < k)
    {
        puts("NO");
    }
    else 
    {
        puts("YES");
        int cnt = 0;
        for (auto [x, v] : mp)
        {
            if (++ cnt > k) break;
            cout << v << ' ';
        }
    }
    
    return 0;
}

AcWing 3989. 看图做题

#include <iostream>
#include <cstring>
#include <algorithm>

using namespace std;

int main()
{
    int n, m;
    scanf("%d%d", &n, &m);
    
    int res = 1, cnt = 1;
    while (cnt != n)
    {
        res += cnt * 12;
        cnt ++ ;
    }
    
    cout << res << endl;
    
    return 0;
}

AcWing 3990. 砍树

#include <iostream>
#include <cstring>
#include <algorithm>

using namespace std;

const int N = 100010, M = N * 2;

int n;
int h[N], e[M], ne[M], idx;
int ans;

void add(int a, int b)
{
    e[idx] = b, ne[idx] = h[a], h[a] = idx ++;
}

int dfs(int u, int father)
{
    int son = 1;
    for (int i = h[u]; ~i; i = ne[i])
    {
        int j = e[i];
        if (j == father) continue;
        int s = dfs(j, u);
        if (s % 2 == 0) ans ++ ;
        son += s;
    }
    return son;
}

int main()
{
    scanf("%d", &n);
    
    if (n % 2)
    {
        puts("-1");
        return 0;
    }
    memset(h, -1, sizeof h);
    for (int i = 0; i < n - 1; i ++ )
    {
        int a, b;
        scanf("%d %d", &a, &b);
        add(a, b), add(b, a);
    }
    
    dfs(1, -1);
    
    cout << ans << endl;
    
    return 0;
}