Educational Codeforces Round 3

这场要是算分的话估计就有机会涨到紫了，4个题1A。

A题：

#include<bits/stdc++.h>
#define REP(i,a,b) for(int i=a;i<=b;i++)
#define MS0(a) memset(a,0,sizeof(a))

using namespace std;

typedef long long ll;
const int maxn=1000100;
const int INF=1<<29;

int n,m;
int a[maxn];

int main()
{
    freopen("in.txt","r",stdin);
    while(cin>>n>>m){
        REP(i,1,n) scanf("%d",&a[i]);
        sort(a+1,a+n+1);
        int ans=0;
        for(int i=n;i>=1;i--){
            if(m<=0) break;
            m-=a[i];
            ans++;
        }
        cout<<ans<<endl;
    }
    return 0;
}

B题：

#include<bits/stdc++.h>
#define REP(i,a,b) for(int i=a;i<=b;i++)
#define MS0(a) memset(a,0,sizeof(a))

using namespace std;

typedef long long ll;
const int maxn=1000100;
const int INF=1<<29;

int n,m;
int a[maxn];
ll cnt[maxn];

ll dfs(int st,int cur)
{
    if(st>=m||cur>m) return 0;
    ll res=cnt[st]*cnt[cur];
    if(cur==m) return res+dfs(st+1,st+2);
    else return res+dfs(st,cur+1);
}

int main()
{
    freopen("in.txt","r",stdin);
    while(cin>>n>>m){
        MS0(cnt);
        REP(i,1,n) scanf("%d",&a[i]),cnt[a[i]]++;
        cout<<dfs(1,2)<<endl;
    }
    return 0;
}

C题：

#include<bits/stdc++.h>
#define REP(i,a,b) for(int i=a;i<=b;i++)
#define MS0(a) memset(a,0,sizeof(a))

using namespace std;

typedef long long ll;
const int maxn=1000100;
const int INF=1<<29;

int n;
int a[maxn];

bool cmp(int a,int b)
{
    return a>b;
}

int main()
{
    freopen("in.txt","r",stdin);
    while(cin>>n){
        ll s=0;
        REP(i,1,n) scanf("%d",&a[i]),s+=a[i];
        sort(a+1,a+n+1,cmp);
        ll ans=0;
        REP(i,1,s%n){
            if(a[i]>s/n+1) ans+=a[i]-(s/n+1);
        }
        REP(i,s%n+1,n){
            if(a[i]>s/n) ans+=a[i]-s/n;
        }
        cout<<ans<<endl;
    }
    return 0;
}

E题：多次询问包括某条边的最小生成树。树链剖分找这条边路径上的最大边权，然后将这条边权去掉就好了。

#include<bits/stdc++.h>
#define REP(i,a,b) for(int i=a;i<=b;i++)
#define MS0(a) memset(a,0,sizeof(a))
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1

using namespace std;

typedef long long ll;
const int maxn=1000100;
const int INF=1<<29;

int n,m;
ll mst;
struct Edge
{
    int u,v;ll w;
    int id;
    friend bool operator<(Edge A,Edge B)
    {
        return A.w<B.w;
    }
};Edge e[maxn];
int Fa[maxn];
struct Tree
{
    int u,v;
    ll w;
};Tree tr[maxn];int trn;
vector<int> G[maxn];
int fa[maxn],dep[maxn],son[maxn],siz[maxn];
int top[maxn];
int id[maxn],num;
ll Max[maxn<<2];
ll val[maxn];

int Find(int x)
{
    return Fa[x]==x?x:Fa[x]=Find(Fa[x]);
}

void dfs1(int u,int f,int d)
{
    fa[u]=f;
    dep[u]=d;
    son[u]=0;
    siz[u]=1;
    for(int i=0;i<G[u].size();i++){
        int v=G[u][i];
        if(v==f) continue;
        dfs1(v,u,d+1);
        if(siz[v]>siz[son[u]]) son[u]=v;
        siz[u]+=siz[v];
    }
}

void dfs2(int u,int tp)
{
    top[u]=tp;
    id[u]=++num;
    if(son[u]) dfs2(son[u],tp);
    for(int i=0;i<G[u].size();i++){
        int v=G[u][i];
        if(v==fa[u]||v==son[u]) continue;
        dfs2(v,v);
    }
}

void push_up(int rt)
{
    Max[rt]=max(Max[rt<<1],Max[rt<<1|1]);
}

void build(int l,int r,int rt)
{
    if(l==r){
        Max[rt]=val[l];
        return;
    }
    int m=(l+r)>>1;
    build(lson);
    build(rson);
    push_up(rt);
}

ll query(int L,int R,int l,int r,int rt)
{
    if(L<=l&&r<=R) return Max[rt];
    int m=(l+r)>>1;
    ll res=-INF;
    if(L<=m) res=max(res,query(L,R,lson));
    if(R>m) res=max(res,query(L,R,rson));
    return res;
}

ll cha(int u,int v)
{
    ll res=-INF;
    while(top[u]!=top[v]){
        if(dep[top[u]]<dep[top[v]]) swap(u,v);
        res=max(res,query(id[top[u]],id[u],1,num,1));
        u=fa[top[u]];
    }
    if(u!=v){
        if(dep[u]>dep[v]) swap(u,v);
        res=max(res,query(id[son[u]],id[v],1,num,1));
    }
    return res;
}

bool cmpID(Edge A,Edge B)
{
    return A.id<B.id;
}

int main()
{
    freopen("in.txt","r",stdin);
    while(cin>>n>>m){
        REP(i,1,m) scanf("%d%d%I64d",&e[i].u,&e[i].v,&e[i].w),e[i].id=i;
        sort(e+1,e+m+1);
        REP(i,1,n) Fa[i]=i;
        mst=0;trn=0;
        REP(i,1,n) G[i].clear();
        REP(i,1,m){
            int x=Find(e[i].u),y=Find(e[i].v);
            if(x!=y){
                Fa[x]=y;
                mst+=e[i].w;
                tr[++trn]={e[i].u,e[i].v,e[i].w};
                G[e[i].u].push_back(e[i].v);
                G[e[i].v].push_back(e[i].u);
            }
        }
        //REP(i,1,trn) cout<<tr[i].u<<" "<<tr[i].v<<" -- "<<tr[i].w<<endl;
        dfs1(1,0,1);
        num=0;
        dfs2(1,1);
        REP(i,1,trn){
            if(dep[tr[i].u]>dep[tr[i].v]) swap(tr[i].u,tr[i].v);
            val[id[tr[i].v]]=tr[i].w;
        }
        build(1,num,1);
        sort(e+1,e+m+1,cmpID);
        REP(i,1,m){
            ll tmp=cha(e[i].u,e[i].v);
            printf("%I64d
",mst-tmp+e[i].w);
        }
    }
    return 0;
}