POJ 2763 Housewife Wind (树链剖分+线段树)

题目链接：POJ 2763 Housewife Wind

题意：抽象出来就是 一棵已知节点之间的边权，两个操作，1·修改边权，2·询问两个节点之间的边权和。

AC代码：

#include <string.h>#include <stdio.h>#include <algorithm>using namespace std;#define lson l,m,rt<<1#define rson m+1,r,rt<<1|1const int maxn=100000+10;const int inf=9999999999;struct Edge{int to,next;};struct Edge edge[maxn*2];int head[maxn],tot;int stree[maxn];//节点v在线段树上的编号int pre[maxn];//在线段树中编号为v节点所对应原图中的编号。int fa[maxn];//f[v] 表示v的父亲节点int son[maxn];//表示 与v同在一重链上的儿子节点（重儿子）int num[maxn];//num[v] v为根的子树的节点数。int top[maxn];//top[v] v所在链的顶端节点。int deep[maxn];//deep[v] 表示v的深度（根的深度为1）int data[maxn];int pos,n;void addedge(int u,int v){edge[tot].to=v;edge[tot].next=head[u];head[u]=tot++;}void dfs1(int u,int father,int dep){int i;deep[u]=dep;fa[u]=father;num[u]=1;for(i=head[u];i!=-1;i=edge[i].next){int v=edge[i].to;if(v!=father){dfs1(v,u,dep+1);num[u]+=num[v];if(son[u]==-1 || num[v]>num[son[u]]){son[u]=v;}}}}//给点编号得到线段树上的对应标号void getpos(int u,int sp){int i;top[u]=sp;stree[u]=pos++;pre[stree[u]]=u;if(son[u]==-1) return ;getpos(son[u],sp);for(i=head[u];i!=-1;i=edge[i].next){int v=edge[i].to;if(v!=son[u] && v!=fa[u]){getpos(v,v);}}}//树状数组or线段树or其他int Max(int a,int b){if(a>b) return a;return b;}struct node{int l,r;int sum,max;};struct node tree[maxn*3];void PushUp(int rt){tree[rt].sum=tree[rt<<1].sum+tree[rt<<1|1].sum;}void build(int l,int r,int rt){tree[rt].l=l;tree[rt].r=r;tree[rt].sum=0;if(l==r){return ;}int m=(tree[rt].l+tree[rt].r)>>1;build(lson);build(rson);PushUp(rt);}void update(int p,int add,int rt){if(tree[rt].l==tree[rt].r && tree[rt].l==p){tree[rt].sum=add;return ;}int m=(tree[rt].l+tree[rt].r)>>1;if(p<=m) update(p,add,rt<<1);else update(p,add,rt<<1|1);PushUp(rt);}int query_sum(int L,int R,int rt){if(L<=tree[rt].l && tree[rt].r<=R){return tree[rt].sum;}int m=(tree[rt].l+tree[rt].r)>>1;int ret=0;if(L<=m) ret+=query_sum(L,R,rt<<1);if(R>m) ret+=query_sum(L,R,rt<<1|1);return ret;}int find_sum(int u,int v){int f1,f2,ans=0;f1=top[u];f2=top[v];while(f1!=f2){//始终f1的深度比f2要大。深度大先更新if(deep[f1]<deep[f2]){swap(f1,f2);swap(u,v);}ans+=query_sum(stree[f1],stree[u],1);u=fa[f1];f1=top[u];}if(u==v) return ans; if(deep[u]>deep[v]) swap(u,v);ans+=query_sum(stree[son[u]],stree[v],1);return ans;}void init(){tot=0;memset(head,-1,sizeof head);pos=0;memset(son,-1,sizeof son);}int e[maxn][5];int main(){ int t,x,y;int q,i,s,tmp;init();scanf("%d%d%d",&n,&q,&s);tmp=s;for(i=0;i<n-1;i++){scanf("%d %d %d",&e[i][0],&e[i][1],&e[i][2]);addedge(e[i][0],e[i][1]);addedge(e[i][1],e[i][0]);}dfs1(1,0,0);//根的deep是0.father从0开始。getpos(1,1);build(1,n,1);for(i=0;i<n-1;i++){if(deep[e[i][0]]>deep[e[i][1]]) swap(e[i][0],e[i][1]);update(stree[e[i][1]],e[i][2],1);}int op;while(q--){int a,b;scanf("%d",&op);if(op==0){scanf("%d",&a);printf("%d\n",find_sum(tmp,a));tmp=a;}else{scanf("%d %d",&a,&b);update(stree[e[a-1][1]],b,1);}}return 0;}