【SPOJ QTREE】树链剖分模板

来源：互联网发布：网络司法拍卖佣金编辑：程序博客网时间：2024/06/05 05:30
用线段树求解，这里注意由于求的是路径最大值，注意一下细节。
#include<cstdio>#include<cstring>#include<algorithm>using namespace std;const int MAXN = 10010;#define lson (pos<<1)#define rson (pos<<1|1)const int INF = (1 << 30);int n;//--------------------------------------------------struct Edge{    int to,next;}edge[MAXN * 2];int head[MAXN],tot;int top[MAXN];int fa[MAXN];int deep[MAXN];int num[MAXN];int p[MAXN];int fp[MAXN];int son[MAXN];int pos;void init(){    tot = 0;    memset(head,-1,sizeof(head));    pos = 1;    memset(son,-1,sizeof(son));}void addedge(int u,int v){    edge[tot].to = v;    edge[tot].next = head[u];    head[u] = tot ++;}void dfs1(int u,int pre,int d){    deep[u] = d;    fa[u] = pre;    num[u] = 1;    for(int i = head[u]; i != -1; i = edge[i].next){        int v = edge[i].to;        if(v != pre){            dfs1(v,u,d + 1);            num[u] += num[v];            if(son[u] == -1 || num[v] > num[son[u]])                son[u] = v; //找重儿子        }    }}void getpos(int u,int sp){    top[u] = sp;    p[u] = pos++;    //printf("%d %d\n",u,p[u]);    fp[p[u]] = u;    if(son[u] == -1) return;    getpos(son[u],sp);    for(int i = head[u]; i != -1; i = edge[i].next){        int v = edge[i].to;        if(v != son[u] && v!= fa[u])            getpos(v,v);    }}//----------------------------------------------int maxv[MAXN << 2];            //该一条边void build(){    memset(maxv,0,sizeof(maxv));}void pushup(int pos){    maxv[pos] = max(maxv[lson],maxv[rson]);}void update(int l,int r,int to,int value,int pos){    if(l == r){        maxv[pos] = value;        return;    }    int mid = (l + r) >> 1;    if(to <= mid)        update(l,mid,to,value,lson);    else        update(mid + 1,r,to,value,rson);    pushup(pos);}int query(int l,int r,int L,int R,int pos){    if(L <= l && r <= R)        return maxv[pos];    int mid = (l + r) >> 1;    int ret = - INF;    if(L <= mid)        ret = max(ret,query(l,mid,L,R,lson));    if(R  > mid)        ret = max(ret,query(mid + 1,r,L,R,rson));    return ret;}//-------------------------------------------------------int find(int u,int v){    int f1 = top[u],f2 = top[v];    int tmp = 0;    while(f1 != f2){        if(deep[f1] < deep[f2]){            swap(f1,f2);            swap(u,v);        }        tmp = max(tmp,query(1,pos,p[f1],p[u],1));        u = fa[f1];        f1 = top[u];    }    if(u == v) return tmp;    if(deep[u] > deep[v]) swap(u,v);    return max(tmp,query(1,pos,p[son[u]],p[v],1));}//----------------------------------------------------------struct E{    int from,to,value;}e[MAXN];int main(){    int T;    int u,v;    scanf("%d",&T);    while(T--){        scanf("%d",&n);        init();        for(int i = 0; i < n - 1; i++){            scanf("%d%d%d",&e[i].from,&e[i].to,&e[i].value);            addedge(e[i].from,e[i].to);            addedge(e[i].to,e[i].from);        }        dfs1(1,0,0);        getpos(1,1);        build();        for(int i = 0; i < n - 1; i++){            if(deep[e[i].from] > deep[e[i].to])                swap(e[i].from,e[i].to);            //这里是更新一条线段，不是一个点            update(1,pos,p[e[i].to],e[i].value,1);        }        char op[10];        while(scanf("%s",op) != EOF){            if(op[0] == 'D') break;            scanf("%d%d",&u,&v);            if(op[0] == 'Q'){                printf("%d\n",find(u,v));            }            else{                update(1,pos,p[e[u - 1].to],v,1);            }        }        if(T) puts("");    }    return 0;}
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