BZOJ 1036 树的统计 树链剖分

写个树链剖分练练手

挺常规的树链剖分，注意这个线段树维护的是每个节点的权值，而不是原图中边的权值，在处理的时候注意一下处理边界就能A了

还有一些小的注意事项详细看注释

#include <cstdio>#include <cstring>#include <iostream>#include <algorithm>#define MAX 30010#define INF 0x7f7f7f7f#define LEFT (pos << 1)#define RIGHT (pos << 1|1)using namespace std;const char qmax[10] = "QMAX";const char qsum[10] = "QSUM";const char change[10] = "CHANGE";struct Complex{int _max,sum;}tree[MAX << 2];int points,asks;int head[MAX],total;int _next[MAX << 1],aim[MAX << 1];int deep[MAX],father[MAX],son[MAX];//PreDFS处理的数组int top[MAX],p[MAX],cnt;//DFS处理的数组char s[10];inline void Add(int x,int y);int PreDFS(int x,int last,int step);void DFS(int x,int last,int t);void Modify(int l,int r,int x,int pos,int num);inline int AskMax(int x,int y);int AskMax(int l,int r,int x,int y,int pos);inline int AskSum(int x,int y);int AskSum(int l,int r,int x,int y,int pos);<span style="white-space:pre"></span>//函数的重载，如果用的话一定要看清楚，别把函数调用错了int main(){cin >> points;for(int x,y,i = 1;i < points; ++i) {scanf("%d%d",&x,&y);Add(x,y),Add(y,x);}PreDFS(1,-1,1);DFS(1,-1,1);for(int x,i = 1;i <= points; ++i) {scanf("%d",&x);Modify(1,cnt,p[i],1,x);}cin >> asks;for(int x,y,i = 1;i <= asks; ++i) {scanf("%s%d%d",s,&x,&y);if(!strcmp(s,qmax))printf("%d\n",AskMax(x,y));if(!strcmp(s,qsum))printf("%d\n",AskSum(x,y));if(!strcmp(s,change))Modify(1,cnt,p[x],1,y);}return 0;}inline void Add(int x,int y){_next[++total] = head[x];aim[total] = y;head[x] = total;}int PreDFS(int x,int last,int step){int max_size = 0,p_son = 0,re = 1;//这里re＝1，每次写都忘记，然后调试出来……千万要记住啊father[x] = last;deep[x] = step;for(int i = head[x];i;i = _next[i]) {if(aim[i] == last)continue;int temp = PreDFS(aim[i],x,step + 1);        re += temp;if(temp > max_size)max_size = temp,p_son = aim[i];}son[x] = p_son;    return re;}void DFS(int x,int last,int t){p[x] = ++cnt;top[x] = t;if(son[x])DFS(son[x],x,t);for(int i = head[x];i;i = _next[i]) {if(aim[i] == last || aim[i] == son[x])continue;DFS(aim[i],x,aim[i]);}}void Modify(int l,int r,int x,int pos,int num){if(l == r && l == x) {tree[pos].sum = tree[pos]._max = num;return ;}int mid = (l + r) >> 1;if(x <= mid)Modify(l,mid,x,LEFT,num);else Modify(mid + 1,r,x,RIGHT,num);tree[pos].sum = tree[LEFT].sum + tree[RIGHT].sum;tree[pos]._max = max(tree[LEFT]._max,tree[RIGHT]._max);}inline int AskMax(int x,int y){int re = -INF;//注意这里的初值int fx = top[x],fy = top[y];while(fx != fy) {if(deep[fx] < deep[fy])swap(fx,fy),swap(x,y);re = max(re,AskMax(1,cnt,p[fx],p[x],1));x = father[fx];fx = top[x];}    if(deep[x] < deep[y])swap(x,y);    re = max(re,AskMax(1,cnt,p[y],p[x],1));return re;}int AskMax(int l,int r,int x,int y,int pos){if(l == x && r == y)return tree[pos]._max;int mid = (l + r) >> 1;if(y <= mid)return AskMax(l,mid,x,y,LEFT);if(x > mid)return AskMax(mid + 1,r,x,y,RIGHT);int left = AskMax(l,mid,x,mid,LEFT);int right = AskMax(mid + 1,r,mid + 1,y,RIGHT);return max(left,right);}inline int AskSum(int x,int y){int re = 0;int fx = top[x],fy = top[y];while(fx != fy) {if(deep[fx] < deep[fy])swap(fx,fy),swap(x,y);re += AskSum(1,cnt,p[fx],p[x],1);x = father[fx];fx = top[x];}    if(deep[x] < deep[y])swap(x,y);    re += AskSum(1,cnt,p[y],p[x],1);return re;}int AskSum(int l,int r,int x,int y,int pos){if(l == x && r == y)return tree[pos].sum;int mid = (l + r) >> 1;if(y <= mid)return AskSum(l,mid,x,y,LEFT);if(x > mid)return AskSum(mid + 1,r,x,y,RIGHT);int left = AskSum(l,mid,x,mid,LEFT);int right = AskSum(mid + 1,r,mid + 1,y,RIGHT);return left + right;}