poj3237(树链剖分边维护+线段树区间更新)

刚开始不会对边进行操作，刚开始一直WA，然后去写了一下spoj375，对边维护的规则熟悉了一下，然而终于发现了错在了哪，原来是要加上u != v。

区间更新的话就是用一个flag值代表，0代表不需取相反数，1代表需要。因为区间取的是最大值，然而最大值取相反数之后就是最小，最小数取相反数就是最大值。所以区间要维护一个最大值和一个最小值

//#include<bits/stdc++.h>#include<iostream>#include<cstdio>#include<algorithm>#include<cstring>using namespace std;typedef long long ll;typedef pair<int,int> P;#define fi first#define se second#define INF 0x3f3f3f3f#define clr(x,y) memset(x,y,sizeof x)#define PI acos(-1.0)#define ITER set<int>::iteratorconst int Mod = 1e9 + 7;const int maxn = 3e4 + 10;struct Edge{    int to,next;}edge[maxn * 2];struct Node{    int x,y,z;}b[maxn * 2];int head[maxn],edge_num,top[maxn],fa[maxn],son[maxn],id[maxn],deq[maxn],siz[maxn],num;int maxs[maxn << 2], mins[maxn << 2],a[maxn],flag[maxn << 2];void add_edge(int x,int y){    edge[edge_num] = (Edge){y,head[x]};    head[x] = edge_num++;}//第一次搜索找出siz[],son[],deq[],fa[]void dfs1(int rt,int pa,int d){    deq[rt] = d;    son[rt] = 0;    fa[rt] = pa;    siz[rt] = 1;    for(int i=head[rt]; i!=-1; i=edge[i].next){        int t = edge[i].to;        if(t != fa[rt]){            dfs1(t,rt,d+1);            siz[rt] += siz[t];            if(siz[son[rt]] < siz[t]){//如果父节点的son[rt]的iz[]小于子节点的siz[]更新son[]                son[rt] = t;            }        }    }}//第二次搜索找到w[],top[]void dfs2(int rt,int tp){    top[rt] = tp;    id[rt] = ++num;    if(son[rt] != 0)        dfs2(son[rt],tp);//如果当前父节点纯在son 那么为了让链在线段树中连续 先对son[]进行搜索，并且重边顶端的点相同。    for(int i=head[rt]; i!=-1; i=edge[i].next){        int t = edge[i].to;        if(t != fa[rt] && son[rt] != t){            dfs2(t,t);        }    }}void fun(int& x,int& y){int t = x;x = -y;y = -t;}void update(int pos,int val,int l,int r,int rt){    if(l == r)    {        maxs[rt] = mins[rt] = val;return ;    }    if(flag[rt])    {        flag[rt << 1] ^= flag[rt];flag[rt <<1|1] ^= flag[rt];        if(flag[rt])fun(mins[rt << 1],maxs[rt <<1]),fun(mins[rt <<1|1],maxs[rt<<1|1]);        flag[rt] = 0;    }    int mid = (l + r) >> 1;    if(pos <= mid)update(pos,val,l,mid,rt << 1);    else if(pos >= mid + 1)update(pos,val,mid + 1,r,rt <<1|1);    maxs[rt] = max(maxs[rt <<1],maxs[rt <<1|1]);mins[rt] = min(mins[rt << 1],mins[rt << 1|1]);}void update1(int L,int R,int l,int r,int rt){    if(L == l && R == r)    {        fun(mins[rt],maxs[rt]);flag[rt] ^= 1;return ;    }    if(flag[rt])    {        flag[rt << 1] ^= flag[rt];flag[rt <<1|1] ^= flag[rt];        if(flag[rt])fun(mins[rt << 1],maxs[rt <<1]),fun(mins[rt <<1|1],maxs[rt<<1|1]);        flag[rt] = 0;    }    int mid = (l + r) >> 1;    if(R <= mid)update1(L,R,l,mid,rt <<1);    else if(L >= mid + 1)update1(L,R,mid + 1,r,rt <<1|1);    else update1(L,mid,l,mid,rt <<1),update1(mid + 1,R,mid + 1,r,rt <<1|1);    maxs[rt] = max(maxs[rt <<1],maxs[rt <<1|1]);mins[rt] = min(mins[rt <<1],mins[rt <<1|1]);}int query(int L,int R,int l,int r,int rt){    if(L == l && R == r)    {        return maxs[rt];    }    if(flag[rt])    {        flag[rt << 1] ^= flag[rt];flag[rt <<1|1] ^= flag[rt];        if(flag[rt])fun(mins[rt << 1],maxs[rt <<1]),fun(mins[rt <<1|1],maxs[rt<<1|1]);        flag[rt] = 0;    }    int mid = (l + r) >> 1;    if(R <= mid)return query(L,R,l,mid,rt << 1);    else if(L >= mid + 1)return query(L,R,mid + 1,r,rt <<1|1);    else return max( query(L,mid,l,mid,rt <<1) , query(mid + 1,R,mid + 1,r,rt <<1|1) );}void updates(int u,int v){    int f1=top[u],f2=top[v];    while(f1!=f2)    {        if(deq[f1]<deq[f2]){            swap(f1,f2);            swap(u,v);        }        update1(id[f1],id[u],2,num,1);        u=fa[f1];f1=top[u];    }    if(deq[u]>deq[v]) swap(u,v);    if(u != v)update1(id[son[u]],id[v],2,num,1);}int solve(int u,int v){    int f1=top[u],f2=top[v];    int ret = -INF;    while(f1!=f2){        if(deq[f1]<deq[f2]){            swap(f1,f2);            swap(u,v);        }//        cout << id[f1] << "   ->   " << id[u] << endl;        ret = max(ret,query(id[f1],id[u],2,num,1));        u=fa[f1];f1=top[u];    }    if(deq[u]>deq[v]) swap(u,v);//    cout << id[u] << "   ->   " << id[v] << endl;    if(u != v)ret = max(ret,query(id[son[u]],id[v],2,num,1));    return ret;}int val[maxn];void Init(){    clr(val,0);    clr(head,-1);edge_num = 0;num = 0;clr(maxs,-INF);clr(mins,INF);clr(flag,0);//0代表正，1代表负}int main(){    int n,m,k;    int Tcase;scanf("%d",&Tcase);    while(Tcase --)    {        scanf("%d",&n);Init();m = n - 1;int cnt = 0;        while(m --){int x,y,z;scanf("%d%d%d",&x,&y,&z);add_edge(x,y);add_edge(y,x);b[++ cnt] = (Node){x,y,z};}        dfs1(1,1,1);dfs2(1,1);        for(int i = 1; i <= n - 1; i ++)        {            if(deq[b[i].x] < deq[b[i].y])swap(b[i].x,b[i].y);            update(id[b[i].x],b[i].z,2,num,1);//            cout << i << " " << " " << b[i].x << " " << id[b[i].x] << endl;        }//        for(int i = 1;i <= n; i ++)cout << i << " --- " << id[i] << endl;        char s[10];int x,y;        while(scanf("%s",s) && s[0] != 'D')        {            scanf("%d%d",&x,&y);            if(s[0] == 'C')            {//                cout << id[b[xC].x] << endl;                update(id[b[x].x],y,2,num,1);            }            else if(s[0] == 'N')            {                updates(x,y);            }            else if(s[0] == 'Q')            {                printf("%d\n",solve(x,y));            }        }    }    return 0;}