G. Mountaineering Squad (violence & dfs)

G.登山小分队(暴力&dfs)

开vectorMaintain the time of people reaching each vertex.每次排序,Update the same time and then merge up.

#include <bits/stdc++.h>
#define int long long
using namespace std;
const int N = 5e5 + 5;
int n, u, v, x;
vector<int> vec[N], g[N];

void dfs(int x, int fa) {
    
    int flag = 1;
    for (auto y : vec[x]) {
    
        if (y == fa)
            continue;
        dfs(y, x);
        flag = 0;
    }
    if (flag)  //叶
        g[x].push_back(0);
    sort(g[x].begin(), g[x].end());

    if (x != 1) {
    
        int len = g[x].size();
        for (int i = 1; i < len; i++)  //当前结点 The processing arrival time is the same
            g[x][i] = max(g[x][i], g[x][i - 1] + 1);
        for (auto v : g[x])  //+1Submit to parent node
            g[fa].push_back(v + 1);
    }
}
signed main() {
    
    cin >> n;
    for (int i = 1; i < n; i++) {
    
        cin >> u >> v;
        vec[u].push_back(v);
        vec[v].push_back(u);
    }
    dfs(1, -1);

    // for (int i = 1; i <= n; i++) {
    
    // cout << i << ":" << endl;
    // for (auto x : g[i])
    // cout << x << " ";
    // cout << endl;
    // }
    cout << g[1][g[1].size() - 1];
    return 0;
}