HDU 3966 - Aragorn's Story(树链剖分)

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题目：

http://acm.hdu.edu.cn/showproblem.php?pid=3966

题意：

n个点的树，每个点都有权值。q个询问：

Q u ：输出u点的权值。I u v d：将u到v的路径上点的权值增加d。D u v d：将u到v的路径上的点的权值减少d。

思路：

树链剖分。修改点权。

相关论文：http://blog.sina.com.cn/s/blog_7a1746820100wp67.html

AC.

#include <iostream>#include <cstdio>#include <cstring>#include <algorithm>using namespace std;const int maxn = 5e4+4;int n, m;int val[maxn];int deep[maxn], fa[maxn], top[maxn], num[maxn], son[maxn], p[maxn], fp[maxn];int pos;int tot, head[maxn];struct Edge{    int to, next;}edge[maxn*2];void init(){    tot = 0;    memset(head, -1, sizeof(head));    pos = 1;    memset(son, -1, sizeof(son));}void addedge(int u, int v){    edge[tot].to = v;    edge[tot].next = head[u];    head[u] = tot++;}int c[maxn];void add(int x, int v){    while(x <= n) {        c[x] += v;        x += x&-x;    }}int sum(int x){    int s = 0;    while(x > 0) {        s += c[x];        x -= x&-x;    }    return s;}void dfs1(int u, int pre, int d){    deep[u] = d;    fa[u] = pre;    num[u] = 1;    for(int i = head[u]; ~i; i = edge[i].next) {        int v = edge[i].to;        if(v == pre) continue;        dfs1(v, u, d+1);        num[u] += num[v];        if(son[u] == -1 || num[v] > num[son[u]]) {            son[u] = v;        }    }}void getpos(int u, int sp){    top[u] = sp;    p[u] = pos++;    fp[p[u]] = u;    if(son[u] == -1) return;    getpos(son[u], sp);    for(int i = head[u]; ~i; i = edge[i].next) {        int v = edge[i].to;        if(v != son[u] && v != fa[u]) {            getpos(v, v);        }    }}void change(int u, int v, int val){    int f1 = top[u], f2 = top[v];    int tmp = 0;    while(f1 != f2) {        if(deep[f1] < deep[f2]) {            swap(f1, f2);            swap(u, v);        }        add(p[f1], val);        add(p[u]+1, -val);        u = fa[f1];        f1 = top[u];    }    if(deep[u] > deep[v]) swap(u, v);    add(p[u], val);    add(p[v]+1, -val);}int main(){   // freopen("in", "r", stdin);    int q;    while(~scanf("%d%d%d", &n, &m, &q)) {        for(int i = 1; i <= n; ++i) {            scanf("%d", &val[i]);        }        init();        for(int i = 0; i < m; ++i) {            int u, v;            scanf("%d%d", &u, &v);            addedge(u, v);            addedge(v, u);        }        dfs1(1, 0, 0);        getpos(1, 1);        memset(c, 0, sizeof(c));        for(int i = 1; i <= n; ++i) {            add(p[i], val[i]);            add(p[i]+1, -val[i]);        }        char op[3];        int u, v, d;        while(q--) {            scanf("%s", op);            if(op[0] == 'Q') {                scanf("%d", &u);                int uu = p[u];                printf("%d\n", sum(uu));            }            else {                scanf("%d%d%d", &u, &v, &d);                if(op[0] == 'D') d = -d;                change(u, v, d);            }        }    }    return 0;}

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