冯志远0911

个人感受：这套题目，跪在了最后一道题，想了许久，应该是7:40左右开始想的，想了斜率优化之类的，但是最后没有拿更多的分数，实在是失策。

三道题100+100+50

nbc

 1 #include<cstdio>
 2 #include<algorithm>
 3 #include<cmath>
 4 #include<cstring>
 5 #include<iostream>
 6 #define mod 1000000007
 7
 8 using namespace std;
 9
10 int n;
11
12 long long ksm(long long a,long long b)
13 {
14     long long ans=1;
15     while (b)
16     {
17         if (b%2==1) ans=ans*a%mod;
18         a=a*a%mod;
19         b/=2;
20     }
21     return ans;
22 }
23 int main()
24 {
25     freopen("nbc.in","r",stdin);
26     freopen("nbc.out","w",stdout);
27
28     scanf("%d",&n);
29     if (n==1) printf("1\n");
30     else
31     {
32         long long y=ksm(2,n-1);
33         long long x=((n-1)*y+1)%mod;
34         long long ans=x*ksm(y,mod-2)%mod;
35         printf("%lld\n",ans);
36
37     }
38 }

original

 1 #include<cstdio>
 2 #include<algorithm>
 3 #include<cmath>
 4 #include<iostream>
 5 #include<cmath>
 6 #define NN 100007
 7 #define MM 200007
 8
 9 using namespace std;
10
11 int n,m;
12 long long k;
13 int fa[NN],size[NN];
14 struct Node
15 {
16     int x,y,z;
17 }a[MM];
18
19 bool cmp(Node x,Node y)
20 {
21     return x.z>y.z;
22 }
23 int find(int num)
24 {
25     if (fa[num]!=num) fa[num]=find(fa[num]);
26     return fa[num];
27 }
28 int main()
29 {
30     freopen("original.in","r",stdin);
31     freopen("original.out","w",stdout);
32
33     scanf("%d%d%lld",&n,&m,&k);
34     for (int i=1;i<=m;i++)
35         scanf("%d%d%d",&a[i].x,&a[i].y,&a[i].z);
36     sort(a+1,a+m+1,cmp);
37     for (int i=1;i<=n;i++)
38     {
39         fa[i]=i;
40         size[i]=1;
41     }
42     long long ans=0;
43     for (int i=1;i<=m;i++)
44     {
45         int x=find(a[i].x),y=find(a[i].y);
46         if (x==y) continue;
47         ans=ans+(long long)size[x]*size[y];
48         if (ans>=k)
49         {
50             printf("%d\n",a[i].z);
51             return 0;
52         }
53         fa[y]=x;
54         size[x]+=size[y];
55     }
56 }

string

 1 #include<cstdio>
 2 #include<algorithm>
 3 #include<iostream>
 4 #include<cmath>
 5 #include<cstring>
 6 #define LL long long
 7 #define NN 2007
 8 #define INF 1e16+7
 9
10 using namespace std;
11
12 int n,a,b,c,d,l,r;
13 LL f[NN],dif[NN],sum[NN];
14 bool boo[NN][NN];
15 char ch[NN];
16
17 void prepare()
18 {
19     scanf("%d%d%d%d%d%d%d",&n,&a,&b,&c,&d,&l,&r);
20     scanf("%s",ch+1);
21     for (int i=1;i<=n;i++)
22     {
23         int mx=0,k[27]={0};
24         for (int j=i;j<=n;j++)
25         {
26             int t=ch[j]-‘a‘;
27             k[t]++;
28             if (k[t]>mx) mx=k[t];
29             if (mx>=l&&mx<=r) boo[i][j]=true;
30         }
31     }
32     for (int i=1;i<=n;i++)
33     {
34         scanf("%lld",&dif[i]);
35         sum[i]=sum[i-1]+dif[i];
36     }
37 }
38 LL fc(LL x)
39 {
40     return (LL)a*x*x+b;
41 }
42 LL fk(LL x)
43 {
44     return (LL)c*x+d;
45 }
46 int main()
47 {
48     freopen("string.in","r",stdin);
49     freopen("string.out","w",stdout);
50
51     prepare();
52
53     for (int i=1;i<=n;i++)
54     {
55         f[i]=INF;
56         for (int j=i-1;j>=0;j--)
57         {
58             f[i]=min(f[i],f[j]+fc(sum[i]-sum[j]));
59             if (boo[j+1][i]) f[i]=min(f[i],f[j]+fk(sum[i]-sum[j]));
60         }
61         printf("%lld\n",f[i]);
62     }
63 }