poj3237 树链部分 边权模板

Tree

Time Limit: 5000MS Memory Limit: 131072KTotal Submissions: 7384 Accepted: 2001

Description

You are given a tree with N nodes. The tree’s nodes are numbered 1 through N and its edges are numbered 1 through N − 1. Each edge is associated with a weight. Then you are to execute a series of instructions on the tree. The instructions can be one of the following forms:

CHANGE i vChange the weight of the ith edge to vNEGATE a bNegate the weight of every edge on the path from a to bQUERY a bFind the maximum weight of edges on the path from a to b

Input

The input contains multiple test cases. The first line of input contains an integer t (t ≤ 20), the number of test cases. Then follow the test cases.

Each test case is preceded by an empty line. The first nonempty line of its contains N (N ≤ 10,000). The next N − 1 lines each contains three integers a, b and c, describing an edge connecting nodes a and b with weight c. The edges are numbered in the order they appear in the input. Below them are the instructions, each sticking to the specification above. A lines with the word “DONE” ends the test case.

Output

For each “QUERY” instruction, output the result on a separate line.

Sample Input

131 2 12 3 2QUERY 1 2CHANGE 1 3QUERY 1 2DONE

Sample Output

13

/*poj3237 树链部分感觉是比较不错的题目，主要是线段树掌握不怎么好导致一直有问题。查询最大值 + 修改边 + 区间置反先处理出树链，然后再上值push_up 和 push_down函数hhh-2016-2-2 3:46:58*/#include <functional>#include <iostream>#include <cstdio>#include <cstdlib>#include <cstring>#include <algorithm>#include <cmath>#include <Map>using namespace std;typedef long long ll;typedef long double ld;using namespace std;const int maxn = 100010;struct node{    int to,next;} edge[maxn*2];int head[maxn];int top[maxn];  //链的顶端节点int far[maxn];  //父亲int dep[maxn];  //深度int num[maxn];  //表示以x为根的子树的节点数int p[maxn];    //p[u]表示边u所在的位置int fp[maxn];   //与p相对应int son[maxn];  //重儿子int tot,pos;void addedge(int u,int v){    edge[tot].to = v;    edge[tot].next = head[u];    head[u] = tot ++;}void dfs(int u,int fa,int d)          //先处理出重儿子、dep、far、num{    dep[u] = d;    far[u] = fa;    num[u] = 1;    for(int i = head[u]; i != -1; i = edge[i].next)    {        int v = edge[i].to;        if(v != fa)        {            dfs(v,u,d+1);            num[u] += num[v];            if(son[u] == -1 || num[v] > num[son[u]])                son[u] = v;        }    }}void getpos(int u,int sp){    top[u] = sp;    p[u] = pos++;    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 != far[u] && v != son[u])            getpos(v,v);    }}struct Node{    int l,r;    int flag;    int Max,Min;} segtree[maxn*3];void build(int i,int l,int r){    segtree[i].l = l;    segtree[i].r = r;    segtree[i].Max = 0;    segtree[i].Min = 0;    segtree[i].flag = 0;    if(l == r)        return ;    int mid = (l+r)/2;    build(i<<1,l,mid);    build((i<<1)|1,mid+1,r);}void push_up(int i){    segtree[i].Max = max(segtree[i<<1].Max,segtree[(i<<1)|1].Max);    segtree[i].Min = min(segtree[i<<1].Min,segtree[(i<<1)|1].Min);}void push_down(int i){    if(segtree[i].l == segtree[i].r)        return ;    if(segtree[i].flag)    {        segtree[i<<1].Max = -segtree[i<<1].Max;        segtree[i<<1].Min = -segtree[i<<1].Min;        swap(segtree[i<<1].Max,segtree[i<<1].Min);        segtree[i<<1].flag ^= 1;        segtree[(i<<1)|1].Max = -segtree[(i<<1)|1].Max;        segtree[(i<<1)|1].Min = -segtree[(i<<1)|1].Min;        segtree[(i<<1)|1].flag ^= 1;        swap(segtree[(i<<1)|1].Max,segtree[(i<<1)|1].Min);        segtree[i].flag = 0;    }}void update(int i,int k,int val){    if(segtree[i].l == k && segtree[i].r == k)    {        segtree[i].Max = val;        segtree[i].Min = val;        segtree[i].flag = 0;        return ;    }    push_down(i);    int mid = (segtree[i].l+segtree[i].r)>>1;    if(k <= mid) update(i<<1,k,val);    else update((i<<1)|1,k,val);    push_up(i);}void negat(int i,int l,int r){    if((segtree[i].l == l && segtree[i].r == r))    {        segtree[i].Max = -segtree[i].Max;        segtree[i].Min = -segtree[i].Min;        swap(segtree[i].Max,segtree[i].Min);        segtree[i].flag ^= 1;        return;    }    push_down(i);    int mid = (segtree[i].l+segtree[i].r)>>1;    if(r <= mid) negat(i<<1,l,r);    else if(l > mid) negat((i<<1)|1,l,r);    else    {        negat(i<<1,l,mid);        negat((i<<1)|1,mid+1,r);    }    push_up(i);}int query(int i,int l,int r){    if(segtree[i].l == l && segtree[i].r == r)    {        return segtree[i].Max;    }    push_down(i);    int mid = (segtree[i].l+segtree[i].r)>>1;    if(r <= mid) return query(i<<1,l,r);    else if(l > mid) return query((i<<1)|1,l,r);    else return max(query(i<<1,l,mid),query((i<<1)|1,mid+1,r));    push_up(i);}int fin(int l,int r){    int f1 = top[l];    int f2 = top[r];    int tt = -100000000;    while(f1 != f2)    {        if(dep[f1] < dep[f2])        {            swap(f1,f2);            swap(l,r);        }        tt = max(query(1,p[f1],p[l]),tt);        l = far[f1];        f1 = top[l];    }    if(l == r)        return tt;    if(dep[l] > dep[r]) swap(l,r);    return max(tt,query(1,p[son[l]],p[r]));}void change(int l,int r){    int f1 = top[l];    int f2 = top[r];    while(f1 != f2)    {        if(dep[f1] < dep[f2])        {            swap(f1,f2);            swap(l,r);        }        negat(1,p[f1],p[l]);        l = far[f1];        f1 = top[l];    }    if(l == r) return ;    if(dep[l] > dep[r]) swap(l,r);    negat(1,p[son[l]],p[r]);}void ini(){    tot = 0;    pos = 1;    memset(head,-1,sizeof(head));    memset(son,-1,sizeof(son));}int me[maxn][2];int va[maxn];int main(){    int T;    int n;    //freopen("in.txt","r",stdin);    scanf("%d",&T);    while(T--)    {        scanf("%d",&n);        ini();        for(int i = 1; i < n; i++)        {            scanf("%d%d%d",&me[i][0],&me[i][1],&va[i]);            addedge(me[i][0],me[i][1]);            addedge(me[i][1],me[i][0]);        }        dfs(1,0,0);        getpos(1,1);        build(1,1,n);        for(int i = 1; i < n; i++)        {            if(dep[me[i][0]] > dep[me[i][1]])                swap(me[i][0],me[i][1]);            update(1,p[me[i][1]],va[i]);        }        char ch[10];        while(scanf("%s",ch) == 1)        {            ;            if(ch[0] == 'D') break;            int u,v;            scanf("%d%d",&u,&v);            if(ch[0] == 'Q')                printf("%d\n",fin(u,v));            else if(ch[0] == 'N')                change(u,v);            else                update(1,p[me[u][1]],v);        }    }    return 0;}