POJ 3237 树链剖分学习(&&树链剖分小结)

一个地方wa了3发，找了一组数组发现的错误，太蠢，就是两个人数作交换写成了 a=b ,b=a。最近智商真是感人。这道题是由spoj375这题改编的，多了一个取反的操作，这个操作只需要多维护一个最小值就行了。然后就是简单的树链剖分+线段树的区间操作。没什么好说的，直接上代码（过几天把LCT学习了，可能回头再来补这题）。

#include <iostream>
#include <cstdio>
#include <cmath>
#include <algorithm>
#include <cstring>
#include <map>
#define LL long long
#define FOR(i,x,y)  for(int i = x;i < y;i ++)
#define IFOR(i,x,y) for(int i = x;i > y;i --)
#define lrt rt<<1
#define rrt rt<<1|1
#define lson rt<<1,l,mid
#define rson rt<<1|1,mid+1,r
#define INF 0x3fffffff
#define MAXN 110000

using namespace std;

int n;

int val0[MAXN],val[MAXN];

int edge_cnt,head[MAXN];

struct Edge{
int u,v,idd;
int nt;
}edge[MAXN<<1];

void add_edge(int u,int v,int idd){
edge[edge_cnt].u = u;
edge[edge_cnt].v = v;
edge[edge_cnt].idd = idd;
edge[edge_cnt].nt = head[u];
head[u] = edge_cnt ++;
}

int top[MAXN],sz[MAXN],fa[MAXN],w[MAXN],son[MAXN],dep[MAXN],id[MAXN];
int totw;
map <int,int> mat;

void dfs1(int u,int father,int depth){
sz[u] = 1; fa[u] = father; dep[u] = depth;
int idd = -1,maxx = -1;
for(int i = head[u];i != -1;i = edge[i].nt){
int v = edge[i].v;
if(v == father) continue;
id[v] = edge[i].idd;
dfs1(v,u,depth+1);
sz[u] += sz[v];
if(sz[v] > maxx){
maxx = sz[v]; idd = v;
}
}
son[u] = idd;
}

void dfs2(int u,int father){
if(son[u] == -1)    return;
top[son[u]] = top[u];
w[son[u]] = ++totw;
val[totw] = val0[id[son[u]]];
mat[id[son[u]]] = totw;
dfs2(son[u],u);
for(int i = head[u];i != -1;i = edge[i].nt){
int v = edge[i].v;
if(v == father) continue;
if(v == son[u]) continue;
top[v] = v;
w[v] = ++totw;
val[totw] = val0[id[v]];
mat[id[v]] = totw;
dfs2(v,u);
}
}

struct Tree{
int l,r;
int maxx,minx;
int lazy;
}tree[MAXN<<2];

void UpDate_Flip(int rt){
tree[rt].lazy ^= 1;
int tem = tree[rt].maxx;
tree[rt].maxx = -tree[rt].minx;
tree[rt].minx = -tem;
}

void PushDown(int rt){
if(tree[rt].lazy){
UpDate_Flip(lrt);
UpDate_Flip(rrt);
tree[rt].lazy = 0;
}
}

void PushUp(int rt){
tree[rt].minx = min(tree[lrt].minx,tree[rrt].minx);
tree[rt].maxx = max(tree[lrt].maxx,tree[rrt].maxx);
}

void Build(int rt,int l,int r){
tree[rt].l = l; tree[rt].r = r;
tree[rt].lazy = 0;
if(l == r){
tree[rt].maxx = tree[rt].minx = val[l];
return;
}
int mid = (l+r)>>1;
Build(lson);
Build(rson);
PushUp(rt);
}

void Modify(int rt,int x,int value){
if(tree[rt].l == tree[rt].r){
tree[rt].maxx = tree[rt].minx = value;
return;
}
PushDown(rt);
int mid = (tree[rt].l + tree[rt].r)>>1;
if(x <= mid)    Modify(lrt,x,value);
else Modify(rrt,x,value);
PushUp(rt);
}

void Negate(int rt,int l,int r){
if(tree[rt].l == l && tree[rt].r == r){
UpDate_Flip(rt);
return;
}
PushDown(rt);
int mid = (tree[rt].l + tree[rt].r)>>1;
if(r <= mid)    Negate(lrt,l,r);
else if(l > mid)    Negate(rrt,l,r);
else{
Negate(lson);
Negate(rson);
}
PushUp(rt);
}

int Query(int rt,int l,int r){
if(tree[rt].l == l && tree[rt].r == r){
return tree[rt].maxx;
}
PushDown(rt);
int mid = (tree[rt].l + tree[rt].r)>>1;
if(r <= mid)    return Query(lrt,l,r);
else if(l > mid)    return Query(rrt,l,r);
else{
return max(Query(lson),Query(rson));
}
}

void C_Negate(int l,int r){
while(top[l] != top[r]){
if(dep[top[l]] >= dep[top[r]]){
Negate(1,w[top[l]],w[l]);
l = fa[top[l]];
}
else{
Negate(1,w[top[r]],w[r]);
r = fa[top[r]];
}
}
if(l == r)  return;
if(dep[l] >= dep[r]){
Negate(1,w[r]+1,w[l]);
}
else Negate(1,w[l]+1,w[r]);
}

int C_Query(int l,int r){
int ans = -INF;
while(top[l] != top[r]){
if(dep[top[l]] >= dep[top[r]]){
ans = max(ans,Query(1,w[top[l]],w[l]));
l = fa[top[l]];
}
else{
ans = max(ans,Query(1,w[top[r]],w[r]));
r = fa[top[r]];
}
}
if(l == r)  return  ans;
if(dep[l] >= dep[r]){
return max(ans,Query(1,w[r]+1,w[l]));
}
else
return max(ans,Query(1,w[l]+1,w[r]));
}

int main()
{
//freopen("test.in","r",stdin);
int T;
scanf("%d",&T);
while(T--){
scanf("%d",&n);
edge_cnt = 0;
memset(head,-1,sizeof(head));
int u,v,value;
FOR(i,1,n){
scanf("%d%d%d",&u,&v,&value);
val0[i] = value;
add_edge(u,v,i);
add_edge(v,u,i);
}
dfs1(1,-1,1);
totw = 0;
top[1] = 1;
dfs2(1,-1);
Build(1,1,totw);
char op[10];
while(~scanf("%s",op) && strcmp(op,"DONE")){
if(!strcmp(op,"QUERY")){
int l,r;
scanf("%d%d",&l,&r);
printf("%d\n",C_Query(l,r));
}
else if(!strcmp(op,"CHANGE")){
int x,value;
scanf("%d%d",&x,&value);
Modify(1,mat[x],value);
}
else{
int l,r;
scanf("%d%d",&l,&r);
C_Negate(l,r);
}
}
}
return 0;
}