BZOJ2157: 旅游

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题目链接

树链剖分的模板题。拿来练一下LCT。。。
pushup中只有当k>n（当前点为边建成的点）时，才能用a[k]更新mx[k]和mn[k]。因为前n个点是没有点权的，统计时只统计边权最大值和最小值，可正可负，所以不能用该点更新。求和则没有影响。

【代码】

 #include <cstdio>#include <iostream>#include <queue>#include <vector>#include <algorithm>#include <cstring>#include <cmath>#define N 40005#define INF 1e9using namespace std;typedef unsigned int ll;typedef pair<ll,ll> pa;int read(){    int x=0,f=1;char ch=getchar();    while(!isdigit(ch)){if(ch=='-') f=-1;ch=getchar();}    while(isdigit(ch)){x=(x<<1)+(x<<3)+ch-'0';ch=getchar();}    return x*f;}int n,m,top;int son[N][2],st[N],fa[N],sum[N],mx[N],mn[N],a[N];bool rev[N],tag[N];void Swap(int k){    tag[k]^=1;a[k]=-a[k];sum[k]=-sum[k];    swap(mn[k],mx[k]);    mn[k]=-mn[k],mx[k]=-mx[k];}void pushup(int k){    int l=son[k][0],r=son[k][1];    mn[k]=min(mn[l],mn[r]);    mx[k]=max(mx[l],mx[r]);    if(k>n) mn[k]=min(mn[k],a[k]);    if(k>n) mx[k]=max(mx[k],a[k]);    sum[k]=sum[l]+sum[r]+a[k];}void pushdown(int k){    int l=son[k][0],r=son[k][1];    if(rev[k])    {        rev[k]=0;rev[l]^=1;rev[r]^=1;        swap(son[k][0],son[k][1]);    }    if(tag[k])    {        if(l) Swap(l);if(r) Swap(r);        tag[k]=0;    }}bool isroot(int x){    return son[fa[x]][0]!=x&&son[fa[x]][1]!=x;}void Rotate(int x){    int y=fa[x],z=fa[y],l,r;    l=son[y][1]==x;r=l^1;    if(!isroot(y)) son[z][son[z][1]==y]=x;    fa[x]=z;fa[y]=x;fa[son[x][r]]=y;    son[y][l]=son[x][r];son[x][r]=y;    pushup(y);pushup(x);}void Splay(int x){    st[++top]=x;    for(int i=x;!isroot(i);i=fa[i]) st[++top]=fa[i];    while(top) pushdown(st[top--]);    while(!isroot(x))    {        int y=fa[x],z=fa[y];        if(!isroot(y)) {            if(son[y][0]==x^son[z][0]==y) Rotate(x);            else Rotate(y);        }        Rotate(x);    }}void Access(int x){    for(int t=0;x;t=x,x=fa[x])        Splay(x),son[x][1]=t,pushup(x);}void Make_Root(int x){    Access(x);Splay(x);rev[x]^=1;}void Split(int x,int y){    Make_Root(x);Access(y);Splay(y);}void Link(int x,int y){    Make_Root(x);fa[x]=y;}void Input_Init(){    n=read();    for(int i=0;i<=n;i++) mn[i]=INF,mx[i]=-INF;    for(int i=1;i<n;i++)    {        static int x,y,z;        x=read()+1,y=read()+1,z=read();        Link(x,i+n);Link(y,i+n);sum[i+n]=mx[i+n]=mn[i+n]=a[i+n]=z;    }}void Solve_Change(int x,int y){    Splay(x);a[x]=y;}void Solve_Negate(int x,int y){    Split(x,y);Swap(y);}void Solve_Sum(int x,int y){    Split(x,y);printf("%d\n",sum[y]);}void Solve_Max(int x,int y){    Split(x,y);printf("%d\n",mx[y]);}void Solve_Min(int x,int y){    Split(x,y);printf("%d\n",mn[y]);}void Solve(){    m=read();    while(m--)    {        char ch[5];static int x,y;        scanf("%s",ch);x=read(),y=read();        if(ch[0]=='C') Solve_Change(x+n,y);        else if(ch[0]=='N') Solve_Negate(x+1,y+1);        else if(ch[0]=='S') Solve_Sum(x+1,y+1);        else if(ch[1]=='A') Solve_Max(x+1,y+1);        else Solve_Min(x+1,y+1);     }}int main(){    Input_Init();    Solve();    return 0;}

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