POJ 2763 Housewife Wind（树链剖分）（线段树单点修改）

#include <iostream>
#include <cstring>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <time.h>
#include <string>
#include <map>
#include <stack>
#include <vector>
#include <set>
#include <queue>
#define met(a,b) memset(a,b,sizeof a)
#define pb push_back
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
using namespace std;
typedef long long ll;
const int N=2e5+50;
const int M=N*N+10;
int dep[N],siz[N],fa[N],id[N],son[N],val[N],top[N]; //top 最近的重链父节点
int num,s,m,n,q;
int sum[N*2],tre[2*N];
vector<int> v[N];
struct tree {
    int x,y,val;
    void read() {
        scanf("%d%d%d",&x,&y,&val);
    }
}e[N];
void dfs1(int u, int f, int d) {
    dep[u] = d;
    siz[u] = 1;
    son[u] = 0;
    fa[u] = f;
    for (int i = 0; i < v[u].size(); i++) {
        int ff = v[u][i];
        if (ff == f) continue;
        dfs1(ff, u, d + 1);
        siz[u] += siz[ff];
        if (siz[son[u]] < siz[ff])
            son[u] = ff;
    }
}
void dfs2(int u, int tp) {
    top[u] = tp;
    id[u] = ++num;
    if (son[u]) dfs2(son[u], tp);
    for (int i = 0; i < v[u].size(); i++) {
        int ff = v[u][i];
        if (ff == fa[u] || ff == son[u]) continue;
        dfs2(ff, ff);
    }
}
inline void PushPlus(int rt) {
    sum[rt]=sum[rt*2]+sum[rt*2+1];
}

void  Build(int l,int r,int rt) {
    if(l==r) {
        sum[rt]=val[l];
        return;
    }
    int m=(l+r)>>1;
    Build(lson);
    Build(rson);
    PushPlus(rt);
    //printf("rt=%d sum[rt]=%d\n",rt,sum[rt]);
}

void Update(int p,int add,int l,int r,int rt) {
    if(l==r) {
        sum[rt]=add;
        return;
    }
    int m=(r+l)>>1;
    if(p<=m)Update(p,add,lson);
    else Update(p,add,rson);
    PushPlus(rt);
}

int Query(int L,int R,int l,int r,int rt) {
    if(L<=l&&r<=R)return sum[rt];
    int m=(l+r)>>1;
    int ans=0;
    if(L<=m)ans+=Query(L,R,lson);
    if(R>m)ans+=Query(L,R,rson);
    return ans;
}

int Yougth(int u, int v) {
    int tp1 = top[u], tp2 = top[v];
    int ans = 0;
    while (tp1 != tp2) {
        if (dep[tp1] < dep[tp2]) {
            swap(tp1, tp2);
            swap(u, v);
        }
        ans += Query(id[tp1], id[u],1,n,1);
        u = fa[tp1];
        tp1 = top[u];
    }
    if (u == v) return ans;
    if (dep[u] > dep[v]) swap(u, v);
    ans += Query(id[son[u]], id[v],1,n,1);
    return ans;
}
void Clear(int n) {
    for(int i=1; i<=n; i++)
        v[i].clear();
}
int main() {
    int u,vv,w;
    scanf("%d%d%d",&n,&q,&s);
    for(int i=1; i<n; i++) {
        e[i].read();
        v[e[i].x].push_back(e[i].y);
        v[e[i].y].push_back(e[i].x);
    }
    num = 0;
    dfs1(1,0,1);
    dfs2(1,1);
    for (int i = 1; i < n; i++) {
        if (dep[e[i].x] < dep[e[i].y]) swap(e[i].x, e[i].y);
        val[id[e[i].x]] = e[i].val;
    }
    Build(1,num,1);
    while(q--) {
        int x;
        scanf("%d",&x);
        if(!x){
            scanf("%d",&u);
            printf("%d\n",Yougth(s,u));
            s=u;
        }
        else {
            scanf("%d%d",&u,&vv);
            Update(id[e[u].x],vv,1,n,1);
        }
    }
    Clear(n);

    return 0;
}