2016秋季练习

来源：互联网发布：金自天正押注人工智能编辑：程序博客网时间：2024/06/10 23:21
来源：lightOJ1011
MST+树链剖分
树剖写挫了RE一个晚上啊
代码：
#include <iostream>#include <cstdio>#include <cstring>#include <algorithm>#include <vector>#define lson rt<<1#define rson rt<<1|1using namespace std;int n,m,Q;const int MAXN = 50010;struct Edge{//Treelink    int nxt,to,w;}edge[MAXN<<2];struct Qnode{//MST    int u,v,w;    inline void input(){        scanf("%d%d%d",&u,&v,&w);    }    inline void get(int uu,int vv,int ww){        u = uu;        v = vv;        w = ww;    }}qnode[MAXN<<2],act[MAXN<<2];int nnn;int cmp(Qnode a,Qnode b){    return a.w<b.w;}int head[MAXN],tot;int sum[MAXN],fa[MAXN],son[MAXN],p[MAXN],dep[MAXN],fp[MAXN],top[MAXN],pos;int gr[MAXN<<1];struct Segment{    int l,r;    int val;}tree[MAXN<<2];inline void ini(){    memset(head,-1,sizeof head);    memset(son,-1,sizeof son);    tot = nnn = pos = 0;}inline void addedge(int u,int v,int w){    edge[tot].to = v;    edge[tot].nxt = head[u];    edge[tot].w = w;    head[u] = tot ++;}int Find(int x){    if(gr[x] == -1) return x;    else return gr[x] = Find(gr[x]);}void kruscal(){    memset(gr,-1,sizeof gr);    sort(qnode+1,qnode+1+m,cmp);    for(int i=1;i<=m;i++){        int u = qnode[i].u;        int v = qnode[i].v;        int w = qnode[i].w;        int f1 = Find(u);        int f2 = Find(v);        if(f1!=f2){            gr[f1] = f2;            addedge(u,v,w);            addedge(v,u,w);            act[++nnn].get(u,v,w);        }    }}void dfs(int rt,int pre,int d){    sum[rt] = 1;    fa[rt] = pre;    dep[rt] = d;    for(int i=head[rt];i!=-1;i=edge[i].nxt){        int now = edge[i].to;        if(now == pre) continue;        dfs(now,rt,d+1);        sum[rt] += sum[now];        if(son[rt] == -1 || sum[now]>sum[son[rt]]) {            son[rt] = now;        }    }}void getpos(int rt,int sp){    top[rt] = sp;    p[rt] = ++pos;    fp[p[rt]] = rt;    if(son[rt]==-1) return ;    getpos(son[rt],sp);    for(int i=head[rt];i!=-1;i=edge[i].nxt){        int now = edge[i].to;        if(now == fa[rt] || now == son[rt]) continue;        getpos(now,now);    }}inline void pushup(int rt){    tree[rt].val = max(tree[lson].val,tree[rson].val);}void build(int rt,int l,int r){    tree[rt].l = l;    tree[rt].r = r;    tree[rt].val = 0;    if(l == r) {        return ;    }    int mid = (l+r)>>1;    build(lson,l,mid);    build(rson,mid+1,r);    pushup(rt);}void update(int rt,int pos,int data){    if(tree[rt].l == pos && pos == tree[rt].r) {        tree[rt].val = data;        return ;    }    int mid = (tree[rt].l+tree[rt].r)>>1;    if(pos<=mid) update(lson,pos,data);    if(pos>=mid+1) update(rson,pos,data);    pushup(rt);}int query(int rt,int l,int r){    if(l<=tree[rt].l  && tree[rt].r<=r){        return tree[rt].val;    }    int mid = (tree[rt].l+tree[rt].r)>>1;    if(r<=mid) return query(lson,l,r);    else if(l>mid) return query(rson,l,r);    else return max(query(lson,l,mid),query(rson,mid+1,r));}int solve(int u,int v){    int ans = -1;    int f1 = top[u];    int f2 = top[v];    while(f1!=f2){        if(dep[f1]<dep[f2]){            swap(f1,f2);            swap(u,v);        }        ans = max(ans,query(1,p[f1],p[u]));        u = fa[f1];        f1 = top[u];    }    if(u == v) return ans;    else if(dep[u]>dep[v]) swap(u,v);    ans = max(ans,query(1,p[son[u]],p[v]));    return ans;}int main(){    int T,nc = 1;    int u,v,w;    int l,r;    scanf("%d",&T);    while(T--){        ini();        scanf("%d%d",&n,&m);        for(int i=1;i<=m;i++){            qnode[i].input();        }        kruscal();        dfs(1,-1,0);        pos = 0;        getpos(1,1);        build(1,1,pos);        for(int i=1;i<=nnn;i++){            int u = act[i].u;            int v = act[i].v;            int cost = act[i].w;            if(dep[u]>dep[v]) swap(u,v);            update(1,p[v],cost);        }        printf("Case %d:\n",nc++);        scanf("%d",&Q);        while(Q--){            scanf("%d%d",&l,&r);            printf("%d\n",solve(l,r));        }    }    return 0;}
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