hdu 3078 Network lca

题目链接

给一棵树， m个操作， 一共两种操作， 将第x个点的权值改为y， 询问x->y路径上权值第k大的点的权值。

暴力的找.....

#include <iostream>
#include <vector>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <map>
#include <set>
#include <string>
#include <queue>
#include <stack>
#include <bitset>
using namespace std;
#define pb(x) push_back(x)
#define ll long long
#define mk(x, y) make_pair(x, y)
#define lson l, m, rt<<1
#define mem(a) memset(a, 0, sizeof(a))
#define rson m+1, r, rt<<1|1
#define mem1(a) memset(a, -1, sizeof(a))
#define mem2(a) memset(a, 0x3f, sizeof(a))
#define rep(i, n, a) for(int i = a; i<n; i++)
#define fi first
#define se second
typedef pair<int, int> pll;
const double PI = acos(-1.0);
const double eps = 1e-8;
const int mod = 1e9+7;
const int inf = 1061109567;
const int dir[][2] = { {-1, 0}, {1, 0}, {0, -1}, {0, 1} };
const int maxn = 1e5+5;
int head[maxn*2], num, f[maxn], deep[maxn], n, val[maxn];
struct node
{
    int to, nextt;
}e[maxn*2];
void add(int u, int v) {
    e[num].to = v, e[num].nextt = head[u], head[u] = num++;
}
void init() {
    num = 0;
    mem1(head);
}
void dfs(int u, int fa) {
    f[u] = fa;
    for(int i = head[u]; ~i; i = e[i].nextt) {
        int v = e[i].to;
        if(v == fa)
            continue;
        deep[v] = deep[u]+1;
        dfs(v, u);
    }
}
int lca(int k, int a, int b)
{
    int i,j;
    vector <int> v;
    if(deep[a]<deep[b])
        swap(a, b);
    while(deep[a]>deep[b]) {
        v.pb(val[a]);
        a = f[a];
    }
    while(a!=b) {
        v.pb(val[a]);
        v.pb(val[b]);
        a = f[a];
        b = f[b];
    }
    v.pb(val[a]);
    if(k>v.size())
        return -1;
    sort(v.begin(), v.end());
    reverse(v.begin(), v.end());
    return v[k-1];
}
int main()
{
    int x, y, m, w, z, sign;
    while(cin>>n>>m) {
        init();
        for(int i = 1; i<=n; i++)
            scanf("%d", &val[i]);
        for(int i = 0; i<n-1; i++) {
            scanf("%d%d", &x, &y);
            add(x, y);
            add(y, x);
        }
        dfs(1, 0);
        while(m--) {
            scanf("%d%d%d", &sign, &x, &y);
            if(!sign) {
                val[x] = y;
            } else {
                int ans = lca(sign, x, y);
                if(~ans)
                    cout<<ans<<endl;
                else
                    puts("invalid request!");
            }
        }
    }
    return 0;
}