FZU 2082 过路费（树链剖分 边权）题解

题意：给出每条边权值，可以更新每条边权值，询问两个点路径的最小权值

思路：重链剖分边权化点权，让每个儿子节点继承边权。

插点权的时候比较边的两个节点的深度，插进儿子节点中。

代码：

#include<cmath>
#include<set>
#include<map>
#include<queue>
#include<cstdio>
#include<vector>
#include<cstring>
#include <iostream>
#include<algorithm>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
const int maxn = 50000 + 5;
const int M = 50 + 5;
const ull seed = 131;
const int INF = 0x3f3f3f3f;
const int MOD = 1000000007;
int fa[maxn];
int top[maxn];
int sz[maxn];
int son[maxn];
int deep[maxn];
int dfn[maxn], tol;
int fd[maxn];

int n, m;
struct Edge{
    int v, w, id, next;
}edge[maxn << 1];
int head[maxn], tot;
void init(){
    memset(head, -1, sizeof(head));
    tot = tol = 0;
    memset(son, -1, sizeof(son));
}
void addEdge(int u, int v, int w, int id){
    edge[tot].v = v;
    edge[tot].w = w;
    edge[tot].id = id;
    edge[tot].next = head[u];
    head[u] = tot++;
}
void dfs1(int u, int pre, int d){
    deep[u] = d;
    fa[u] = pre;
    sz[u] = 1;
    for(int i = head[u]; i != -1; i = edge[i].next){
        int v = edge[i].v;
        if(v == pre) continue;
        dfs1(v, u, d + 1);
        sz[u] += sz[v];
        if(son[u] == -1 || sz[v] > sz[son[u]])
            son[u] = v;
    }
}
void dfs2(int u, int tp){
    top[u] = tp;
    dfn[u] = ++tol;
    fd[tol] = u;
    if(son[u] == -1) return;
    dfs2(son[u], tp);
    for(int i = head[u]; i != -1; i = edge[i].next){
        int v = edge[i].v;
        if(v != son[u] && v != fa[u]){
            dfs2(v, v);
        }
    }
}

ll sum[maxn << 2];
void update(int pos, int l, int r, int v, int rt){
    if(l == r){
        sum[rt] = v;
        return;
    }
    int m = (l + r) >> 1;
    if(pos <= m)
        update(pos, l, m, v, rt << 1);
    else
        update(pos, m + 1, r, v, rt << 1 | 1);
    sum[rt] = sum[rt << 1] + sum[rt << 1 | 1];
}
ll query(int L, int R, int l, int r, int rt){
    if(L <= l && R >= r){
        return sum[rt];
    }
    int m = (l + r) >> 1, ans = 0;
    if(L <= m)
        ans += query(L, R, l, m, rt << 1);
    if(R > m)
        ans += query(L, R, m + 1, r, rt << 1 | 1);
    sum[rt] = sum[rt << 1] + sum[rt << 1 | 1];
    return ans;
}

ll change(int u, int v){
    ll ret = 0;
    while(top[u] != top[v]){
        if(deep[top[u]] < deep[top[v]]) swap(u, v);
        ret += query(dfn[top[u]], dfn[u], 1, n, 1);
        u = fa[top[u]];
    }
    if(u == v) return ret;  //!!!
    if(deep[u] > deep[v]) swap(u, v);
    ret += query(dfn[son[u]], dfn[v], 1, n, 1);
    return ret;
}
int e[maxn][3];
int main(){
    while(~scanf("%d%d", &n, &m)){
        init();
        for(int i = 1; i <= n - 1; i++){
            int u, v, w;
            scanf("%d%d%d", &u, &v, &w);
            addEdge(u, v, w, i);
            addEdge(v, u, w, i);
            e[i][0] = u, e[i][1] = v, e[i][2] = w;
        }
        dfs1(1, 0, 0);
        dfs2(1, 1);
        for(int i = 1; i <= n - 1; i++){
            int fx = e[i][0], fy = e[i][1];
            if(deep[fx] < deep[fy]) swap(fx, fy);
            update(dfn[fx], 1, n, e[i][2], 1);
        }
        while(m--){
            int op, a, b;
            scanf("%d%d%d", &op, &a, &b);
            if(op == 0){
                int fx = e[a][0], fy = e[a][1];
                if(deep[fx] < deep[fy]) swap(fx, fy);
                update(dfn[fx], 1, n, b, 1);
            }
            else{
                printf("%lld
", change(a, b));
            }
        }
    }
    return 0;
}