Codeforces Round #425 (Div. 2)比赛总结

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心累。。上次写的总结不知道怎么搞的被吞了。。只能再写一遍了。。
这次就写BCD吧。。
B题是阅读题，写程序什么的不难。注意细节。。

#include<iostream>#include<set>#include<string>#include<cstring>using namespace std;int main(){    char s[30];    cin >> s;    set<char>S;    set<int>Index;    for (int i = 0;i < strlen(s);i++)        S.insert(s[i]);    string a;    cin >> a;    int bad=-1;    for (int i = 0;i < a.size();i++)    {        if (a[i] == '?')Index.insert(i);        else if (a[i] == '*')bad = i;    }    int t;    cin >> t;    string temp;    for (int i = 0;i < t;i++)    {        cin >> temp;        bool flag = true;        if (temp.size() == a.size())        {            for (int j = 0;j < temp.size();j++)            {                if (Index.count(j) && !S.count(temp[j])) { flag = false;break; }                else if (j != bad && !Index.count(j) && temp[j] != a[j]) { flag = false;break; }                else if (j == bad&&S.count(temp[j])) { flag = false;break; }            }        }        else if (temp.size() > a.size())        {            if (bad == -1) { flag = false; }            else            {                int thebad = bad;                for (int j = 0;j < thebad;j++)                {                    if (Index.count(j) && !S.count(temp[j])) { flag = false;break; }                    else if (!Index.count(j) && temp[j] != a[j]) { flag = false;break; }                }                int Left = temp.size() - a.size();                int j;                for ( j = thebad;j <= thebad + Left;j++)                {                    if (S.count(temp[j])) { flag = false;break; }                }                for (int k = thebad + 1;k < a.size();k++, j++)                {                    if (Index.count(k) && !S.count(temp[j])) { flag = false;break; }                    else if ( !Index.count(k) && temp[j] != a[j]) { flag = false;break; }                }            }        }        else        {            if (a.size() - temp.size() > 1)flag = false;            else            {                int thebad = bad;                int j;                for ( j = 0;j < thebad;j++)                {                    if (Index.count(j) && !S.count(temp[j])) { flag = false;break; }                    else if ( !Index.count(j) && temp[j] != a[j]) { flag = false;break; }                }                for (int k = thebad + 1;k < a.size();k++, j++)                {                    if (Index.count(k) && !S.count(temp[j])) { flag = false;break; }                    else if (!Index.count(k) && temp[j] != a[j]) { flag = false;break; }                }            }        }        if (flag)cout << "YES" << endl;        else cout << "NO" << endl;    }    return 0;}

C题二分时间不难

#include<iostream>#include<stdio.h>#include<algorithm>#include<math.h>using namespace std;typedef long long ll;struct node{    int x,v,dir;} nodes[100005];int n,s;bool check(double limit){    bool Left=false,Right=false;    long long Leftl=(ll)1e6,LeftR=0,Rightl=(ll)1e6,RightR=0;    for(int i=1; i<=n; i++)    {       //if(Left&&Right)break;        if(nodes[i].dir==1)        {            double temp=limit*(nodes[i].v+s);            if(temp>=nodes[i].x)Left=true;            else continue;            temp=limit*nodes[i].v;            double v=nodes[i].v;            if(temp>=nodes[i].x){Leftl=0;LeftR=1e6;continue;}            else            {                 double min_time=(double)(nodes[i].x-limit*nodes[i].v)/s;//最少需要有多少时间有光速的加成                ll lo=nodes[i].x+floor((limit-min_time)*(s-nodes[i].v));//这种情况下炸弹最右的位置                Leftl=min(Leftl,(ll)(nodes[i].x));                LeftR=max(LeftR,lo);            }        }        else        {            double temp=limit*(nodes[i].v+s);            if(temp>=(1e6-nodes[i].x))Right=true;            else continue;            temp=limit*nodes[i].v;            double v=nodes[i].v;            if(temp>=(1e6-nodes[i].x)){Rightl=0;RightR=1e6;continue;}            else            {                 double min_time=(double)(1e6-nodes[i].x-nodes[i].v*limit)/s;                ll lo=nodes[i].x-floor((limit-min_time)*(s-nodes[i].v));                Rightl=min(Rightl,lo);                RightR=max(RightR,(ll)nodes[i].x);            }        }    }    if(!Left||!Right)return false;    if(Leftl>LeftR||Rightl>RightR)return false;    return !(Leftl>RightR||Rightl>LeftR);}int main(){    scanf("%d%d",&n,&s);    for(int i=1; i<=n; i++)    {        scanf("%d%d%d",&nodes[i].x,&nodes[i].v,&nodes[i].dir);    }    double l=0;    double r=1e6;    double mid;    double ans;    for(int i=1; i<=50; i++)    {        mid=(l+r)/2.0;        if(check(mid))        {            r=mid;            ans=mid;        }        else l=mid;    }    printf("%.7f\n",ans );    return 0;}

D题 lca模版题有点难。。毕竟第一次做lca

#include<iostream>#include<math.h>#include<stdio.h>#include<cstring>using namespace std;const int N=100005;const int M=25;int _pow[M];int head[N];int ver[2*N];int R[2*N];int first[N];int dir[N];int dp[2*N][M];bool vis[N];int tot;int cnt;struct edge{    int u,v,w,next;}e[2*N];void dfs(int u,int dep){    vis[u]=true;ver[++tot]=u;first[u]=tot;R[tot]=dep;    for(int k=head[u];k!=-1;k=e[k].next)        if(!vis[e[k].v])    {        int v=e[k].v,w=e[k].w;        dir[v]=dir[u]+w;        dfs(v,dep+1);        ver[++tot]=u;        R[tot]=dep;    }}void ST(int len){    int K=(int)(log((double)len)/log(2.0));    for(int i=1;i<=len;i++)dp[i][0]=i;    for(int j=1;j<=K;j++)        for(int i=1;i+_pow[j]-1<=len;i++)    {        int a=dp[i][j-1],b=dp[i+_pow[j-1]][j-1];        if(R[a]<R[b])dp[i][j]=a;        else dp[i][j]=b;    }}int RMQ(int x,int y){    int K=(int)(log((double)(y-x+1))/log(2.0));    int a=dp[x][K],b=dp[y-_pow[K]+1][K];    if(R[a]<R[b])return a;    else return b;}int LCA(int u,int v){    int x=first[u],y=first[v];    if(x>y)swap(x,y);    int res=RMQ(x,y);    return ver[res];}void addedge(int u,int v){    e[cnt].u=u;    e[cnt].v=v;    e[cnt].w=1;    e[cnt].next=head[u];    head[u]=cnt++;}int getdis(int u,int v){    int fa=LCA(u,v);    return dir[u]+dir[v]-2*dir[fa];}void init(){    for(int i=0;i<=M;i++)        _pow[i]=(1<<i);    memset(head,-1,sizeof(head));}int main(){    init();    int n,q;    int p;    scanf("%d%d",&n,&q);    for(int i=2;i<=n;i++)    {        scanf("%d",&p);        addedge(i,p);        addedge(p,i);    }    dfs(1,1);    ST(tot);    int a,b,c;    for(int i=1;i<=q;i++)    {        scanf("%d%d%d",&a,&b,&c);        int dis1=getdis(a,b);        int dis2=getdis(a,c);        int dis3=getdis(b,c);        int len1=(dis1+dis2-dis3)/2+1;        int len2=(dis1+dis3-dis2)/2+1;        int len3=(dis2+dis3-dis1)/2+1;        printf("%d\n",max(len1,max(len2,len3)));    }    return 0;}

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