SPOJ GRASSPLA Grass Planting

题目：http://www.spoj.com/problems/GRASSPLA/en/

题意：给定一棵树，树有边权，初始边权都为0。有两种操作：第一种是两点之间的边权均加1，第二种是求两点之间的边权和。

思路：树链剖分啊，线段树区间求和。写成多实例一直莫名RE，改成单实例就过了

#include <iostream>#include <cstdio>#include <cstring>#include <algorithm>using namespace std;typedef long long ll;const int INF = 0x3f3f3f3f;const int N = 100010;struct edge{    int to, next;} g[N*2];struct node{    int l, r;    ll sum, mark;} s[N*4];int dep[N], top[N], son[N], siz[N], fat[N], id[N], head[N];int n, m, cnt, num;void add_edge(int v, int u){    g[cnt].to = u;    g[cnt].next = head[v];    head[v] = cnt++;}void dfs1(int v, int fa, int d){    dep[v] = d, siz[v] = 1, fat[v] = fa, son[v] = 0;    for(int i = head[v]; i != -1; i = g[i].next)    {        int u = g[i].to;        if(u != fa)        {            dfs1(u, v, d + 1);            siz[v] += siz[u];            if(siz[son[v]] < siz[u]) son[v] = u;        }    }}void dfs2(int v, int tp){    top[v] = tp, id[v] = ++num;    if(son[v]) dfs2(son[v], tp);    for(int i = head[v]; i != -1; i = g[i].next)    {        int u = g[i].to;        if(u != fat[v] && u != son[v]) dfs2(u, u);    }}void push_up(int k){    s[k].sum = s[k<<1].sum + s[k<<1|1].sum;}void push_down(int k){    if(s[k].mark)    {        s[k<<1].mark += s[k].mark;        s[k<<1|1].mark += s[k].mark;        s[k<<1].sum += (s[k<<1].r - s[k<<1].l + 1) * s[k].mark;        s[k<<1|1].sum += (s[k<<1|1].r - s[k<<1|1].l + 1) * s[k].mark;        s[k].mark = 0;    }}void build(int l, int r, int k){    s[k].l = l, s[k].r = r, s[k].mark = 0, s[k].sum = 0;    if(l == r) return;    int mid = (l + r) >> 1;    build(l, mid, k << 1);    build(mid + 1, r, k << 1|1);    push_up(k);}void update(int l, int r, int k){    if(l <= s[k].l && s[k].r <= r)    {        s[k].sum += s[k].r - s[k].l + 1;        s[k].mark += 1;        return;    }    push_down(k);    int mid = (s[k].l + s[k].r) >> 1;    if(l <= mid) update(l, r, k << 1);    if(r > mid) update(l, r, k << 1|1);    push_up(k);}void renew(int v, int u){    int t1 = top[v], t2 = top[u];    while(t1 != t2)    {        if(dep[t1] < dep[t2])            swap(t1, t2), swap(v, u);        update(id[t1], id[v], 1);        v = fat[t1], t1 = top[v];    }    if(v == u) return;    if(dep[v] > dep[u]) swap(v, u);    update(id[son[v]], id[u], 1);}ll query(int l, int r, int k){    if(l <= s[k].l && s[k].r <= r)        return s[k].sum;    push_down(k);    int mid = (s[k].l + s[k].r) >> 1;    ll ans = 0;    if(l <= mid) ans += query(l, r, k << 1);    if(r > mid) ans += query(l, r, k << 1|1);    push_up(k);    return ans;}ll seek(int v, int u){    int t1 = top[v], t2 = top[u];    ll ans = 0;    while(t1 != t2)    {        if(dep[t1] < dep[t2])            swap(t1, t2), swap(v, u);        ans += query(id[t1], id[v], 1);        v = fat[t1], t1 = top[v];    }    if(v == u) return ans;    if(dep[v] > dep[u]) swap(v, u);    return ans + query(id[son[v]], id[u], 1);}void slove(){    char ch;    int a, b;    while(m--)    {        scanf(" %c%d%d", &ch, &a, &b);        if(ch == 'P') renew(a, b);        else printf("%lld\n", seek(a, b));    }}int main(){    int a, b;    scanf("%d%d", &n, &m);    memset(head, -1, sizeof head);    cnt = num = 0;    for(int i = 1; i <= n - 1; i++)    {        scanf("%d%d", &a, &b);        add_edge(a, b);        add_edge(b, a);    }    dfs1(1, 0, 1);    dfs2(1, 1);    build(1, num, 1);    slove();    return 0;}