2018年浙江理工大学程序设计竞赛校赛 Problem I: 沙僧

沙僧

思路：

dfs序+差分数组

分层考虑，通过dfs序来查找修改的区间段，然后用差分数组修改

代码：

#include<bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define pi acos(-1.0)
#define LL long long
#define mp make_pair
#define pb push_back
#define ls rt<<1, l, m
#define rs rt<<1|1, m+1, r
#define ULL unsigned LL
#define pll pair<LL, LL>
#define pii pair<int, int>
#define piii pair<int,pii>
#define mem(a, b) memset(a, b, sizeof(a))
#define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout);
//head

const int N = 1e5 + 5;
int deep[N], l[N], r[N];
LL ans[N];
vector<int>g[N];
vector<int>d[N];
vector<LL>v[N];
vector<int>t[N];
int x = 0;
void dfs(int o, int u, int dd) {
    deep[u] = dd;
    d[dd].pb(x);
    t[dd].pb(u);
    v[dd].pb(0);
    l[u] = x;
    for (int i = 0; i < g[u].size(); i++) {
        if(g[u][i] != o) {
            ++x;
            dfs(u, g[u][i], dd+1);
        }
    }
    r[u] = x;
}
int main() {
    int n, m, a, b, c;
    scanf("%d %d", &n, &m);
    for (int i = 1; i < n; i++) {
        scanf("%d %d", &a, &b);
        g[a].pb(b);
        g[b].pb(a);
    }
    ++x;
    dfs(1, 1, 0);
    while(m --) {
        scanf("%d %d %d", &a, &b, &c);
        int pos = deep[a] + b;
        if(pos >= N || d[pos].size() == 0) continue;
        int st = lower_bound(d[pos].begin(), d[pos].end(), l[a]) - d[pos].begin();
        int ed = upper_bound(d[pos].begin(), d[pos].end(), r[a]) - d[pos].begin();
        v[pos][st] += c;
        if(ed < v[pos].size()) v[pos][ed] -= c;
    }
    for (int i = 0; i <= n; i++) {
        if(v[i].size() == 0) break;
        ans[t[i][0]] = v[i][0];
        for (int j = 1; j < v[i].size(); j++) {
            v[i][j] += v[i][j-1];
            ans[t[i][j]] = v[i][j];
        }
    }
    for (int i = 1; i <= n; i++) printf("%lld%c", ans[i], " \n"[i==n]);
    return 0;
}

/*
7 2
1 2
1 3
2 4
2 5
3 6
3 7
2 1 2
3 1 2
*/