Spoj qtree 375. Query on a tree, spojqtree

Spoj qtree 375. Query on a tree, spojqtree

SPOJ Problem Set (classical) 375. Query on a treeProblem code: QTREE

You are given a tree (an acyclic undirected connected graph) NNodes, and edges numbered 1, 2, 3... N-1.

We will ask you to perfrom some instructions of the following form:

• CHANGE I ti: Change the cost of the I-th edge to ti
  Or
• QUERY a B: Ask for the maximum edge cost on the path from node a to node B

Input

The first line of input contains an integerT, The number of test cases (T<= 20). t test cases follow.

For each test case:

• In the first line there is an integerN(N<= 10000 ),
• In the nextN-1 lines, the I-th line describes the I-th edge: a line with three integersA B cDenotes an edgeA,BOf costC(C<= 1000000 ),
• The next lines contain instructions"CHANGE I ti"Or"QUERY a B",
• The end of each test case is signiied by the string"DONE".

There is one blank line between successive tests.

Output

For each"QUERY"Operation, write one integer representing its result.

Example

Input:131 2 12 3 2QUERY 1 2CHANGE 1 3QUERY 1 2DONEOutput:13

Added:	Thanh-Vy Hua
Date:
Time limit:	5S
Source limit:	15000B
Memory limit:	256 MB
Cluster:	Pyramid (Intel Pentium III 733 MHz)
Ages:	All protocol T: awk c ++ 4.3.2 C99 strict cloj erl f # go js nodejs perl 6 PYTH 3.2.3 PYTH 3.2.3 n SCALA SED TCL

Tree link splitting + line segment tree

Maintain the maximum edge weight on the two-point path...

#include <iostream>#include <cstring>#include <cstdio>#include <algorithm>using namespace std;typedef long long int LL;const int maxn=110000;struct Edge{int to,next;}edge[maxn*4];int Adj[maxn],Size;void init_edge(){memset(Adj,-1,sizeof(Adj)); Size=0;}void add_edge(int u,int v){edge[Size].to=v; edge[Size].next=Adj[u]; Adj[u]=Size++;}int fa[maxn],deep[maxn],num[maxn],son[maxn];int top[maxn],p[maxn],rp[maxn],pos;void init(){init_edge();memset(son,-1,sizeof(son));pos=1;}void dfs1(int u,int pre,int d){num[u]=1; fa[u]=pre; deep[u]=d;for(int i=Adj[u];~i;i=edge[i].next){int v=edge[i].to;if(v==pre) continue;dfs1(v,u,d+1);num[u]+=num[v];if(son[u]==-1||num[son[u]]<num[v])son[u]=v;}}void getPOS(int u,int to){top[u]=to;p[u]=pos++;rp[p[u]]=u;if(son[u]!=-1) getPOS(son[u],to);for(int i=Adj[u];~i;i=edge[i].next){int v=edge[i].to;if(v!=fa[u]&&v!=son[u])getPOS(v,v);}}int n;int e[maxn][3];///segTree#define lson l,m,rt<<1#define rson m+1,r,rt<<1|1int maxnum[maxn<<2];void build(int l,int r,int rt){    maxnum[rt]=0;    if(l==r) return ;    int m=(l+r)/2;    build(lson);    build(rson);}void push_up(int rt){    maxnum[rt]=max(maxnum[rt<<1],maxnum[rt<<1|1]);}void update(int pos,int val,int l,int r,int rt){    if(l==pos&&r==pos)    {        maxnum[rt]=val;        return ;    }    int m=(l+r)/2;    if(pos<=m) update(pos,val,lson);    else update(pos,val,rson);    push_up(rt);}int query(int L,int R,int l,int r,int rt){    if(L<=l&&r<=R)    {        return maxnum[rt];    }    int m=(l+r)/2;    int ret=0;    if(L<=m) ret=max(ret,query(L,R,lson));    if(R>m) ret=max(ret,query(L,R,rson));    return ret;}int find(int u,int v){    int f1=top[u],f2=top[v];    int ret=0;    while(f1!=f2)    {        if(deep[f1]<deep[f2])        {            swap(f1,f2); swap(u,v);        }        ret=max(ret,query(p[f1]-1,p[u]-1,1,n,1));        u=fa[f1]; f1=top[u];    }    if(u==v) return ret;    if(deep[u]>deep[v]) swap(u,v);    ret=max(ret,query(p[son[u]]-1,p[v]-1,1,n,1));    return ret;}void showit(int l,int r,int rt){    cout<<rt<<": "<<l<<" <---> "<<r<<"  max: "<<maxnum[rt]<<endl;    if(l==r) return ;    int m=(l+r)/2;    showit(lson); showit(rson);}int main(){    int T_T;    scanf("%d",&T_T);    while(T_T--)    {        scanf("%d",&n);        init();        n--;        for(int i=1;i<=n;i++)        {            int a,b,c;            scanf("%d%d%d",&a,&b,&c);            e[i][0]=a;e[i][1]=b;e[i][2]=c;            add_edge(a,b);            add_edge(b,a);        }        dfs1(1,1,0);        getPOS(1,1);        build(1,n,1);        for(int i=1;i<=n;i++)        {            if(deep[e[i][0]]>deep[e[i][1]])                swap(e[i][0],e[i][1]);            update(p[e[i][1]]-1,e[i][2],1,n,1);        }        char op[10];        while(scanf("%s",op)!=EOF)        {            if(op[0]=='Q')            {                int a,b;                scanf("%d%d",&a,&b);                printf("%d\n",find(a,b));            }            else if(op[0]=='C')            {                int a,b;                scanf("%d%d",&a,&b);                update(p[e[a][1]]-1,b,1,n,1);            }            else if(op[0]=='D')            {                putchar(10);                break;            }        }    }return 0;}