AT2148 [ARC063C] 木と整数 / Integers on a Tree

https://www.luogu.com.cn/problem/AT2148

考虑维护一个堆，每次拿出最上面一个，然后把和它相邻的点设为$val[u]-1$

最后check一遍即可，容易怎么这个一定是正确的

code:

#include<bits/stdc++.h>
#define N 200050
using namespace std;
struct edge {
    int v, nxt;
} e[N << 1];
int p[N], eid;
void init() {
    memset(p, -1, sizeof p);
    eid = 0;
}
void insert(int u, int v) {
    e[eid].v = v;
    e[eid].nxt = p[u];
    p[u] = eid ++;
}
const int INF = 1e9;
priority_queue<pair<int, int> > q;
int f, n, val[N], m;
void dfs(int u, int fa) {
    for(int i = p[u]; i + 1; i = e[i].nxt) {
        int v = e[i].v;
        if(abs(val[u] - val[v]) != 1) f = 1;
        if(v == fa) continue;
        dfs(v, u);
    }
}
int main() {
    init();
    scanf("%d", &n);
    for(int i = 1; i <= n; i ++) val[i] = INF;
    for(int i = 1; i < n; i ++) {
        int u, v;
        scanf("%d%d", &u, &v);
        insert(u, v), insert(v, u);
    }
    scanf("%d", &m);
    while(m --) {
        int x, y;
        scanf("%d%d", &x, &y);
        val[x] = y;
        q.push(make_pair(y, x));
    }
    while(q.size()) {
        int u = q.top().second; q.pop();
        for(int i = p[u]; i + 1; i = e[i].nxt) {
            int v = e[i].v;
            if(val[v] == INF) val[v] = val[u] - 1, q.push(make_pair(val[v], v));
        }
    }
    dfs(1, 0);
    if(f) printf("No");
    else {
        printf("Yes\n");
        for(int i = 1; i <= n; i ++) printf("%d\n", val[i]);
    }
    return 0;
}