AtCoder Beginner Contest 087

A

模拟题，直接减去之后直接进行取余即可。

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#include<bits/stdc++.h>
    using namespace std;

    int main()
    {
        int x,a,b;
        while(cin>>x>>a>>b){
            x-=a;
            x%=b;
            cout<<x<<endl;
        }
        return 0;
    }

B

暴力。

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#include<bits/stdc++.h>
    using namespace std;

    int main()
    {
        int x,a,b,c;
        while(cin>>a>>b>>c>>x){
            x/=50;
            int sum=0;
            for(int i=0;i<=a;i++){
                for(int j=0;j<=b;j++){
                    for(int k=0;k<=c;k++){
                        if(i*10+j*2+k==x) sum++;
                    }
                }
            }
            cout<<sum<<endl;
        }
        return 0;
    }

C

两次前缀和也是显而易见了。

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#include <bits/stdc++.h>
using namespace std;
int a[101], b[101];
int suma[101], sumb[101];
int main()
{
    int n;
    while (cin >> n)
    {
        for (int i = 0; i < n; i++)
        {
            cin >> a[i];
        }
        for (int i = 0; i < n; i++)
        {
            cin >> b[i];
        }
        suma[0] = a[0];
        sumb[0] = b[0];
        for (int i = 1; i < n; i++)
        {
            suma[i] = suma[i - 1] + a[i];
            sumb[i] = sumb[i - 1] + b[i];
        }
        int maxn = suma[0] + sumb[n - 1];
        for (int i = 1; i < n; i++)
        {
            int sum = suma[i] + sumb[n - 1] - sumb[i - 1];
            maxn = max(maxn, sum);
        }
        cout << maxn << endl;
    }
    return 0;
}

D

带权并查集。dis[l]表示l到祖先的距离。

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#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ull = unsigned long long;
const int N = 1e5 + 100;
int fa[N];
int dis[N];
int find(int x)
{
    if (fa[x] != x)
    {
        int nf = fa[x];
        fa[x] = find(fa[x]);
        dis[x] += dis[nf];
    }
    return fa[x];
}
int main()
{
    int n, m;
    cin >> n >> m;
    for (int i = 1; i <= n; i++)
    {
        fa[i] = i;
    }
    bool flag = 1;
    for (int i = 1; i <= m; i++)
    {
        int l, r, d;
        cin >> l >> r >> d;
        int la = find(l);
        int lr = find(r);
        if (la == lr)
        {
            if (dis[l] - dis[r] != d)
            {
                flag = 0;
            }
        }
        else
        {
            fa[la] = lr;
            dis[la] = d + dis[r] - dis[l];
        }
    }

    if (flag)
    {
        cout << "Yes" << '\n';
    }
    else
    {
        cout << "No" << '\n';
    }
    return 0;
}