P3884 [JLOI2009]二叉树问题

题意：给你一个二叉树，输出它的深度，宽度，以及对于结点u和v输出它们的距离
u和v的距离定义：设u和v的最近公共祖先为c，dist(u, v) = dist(u, c) * 2 + dist(v, c);

#include<iostream>
#include<algorithm>
#include<cstring>

using namespace std;

const int N = 110;

int n;
int cnt[N], st[N];
int h[N], e[N], ne[N], idx;
int p[N]; // 结点的双亲结点
int w, d; // 宽度，深度

void add(int a, int b){
    e[idx] = b, ne[idx] = h[a], h[a] = idx ++;
}

int dfs(int u, int l){
    st[u] = 1;
    cnt[l] ++;
    w = max(cnt[l], w);
    d = max(l, d);
    for(int i = h[u]; i != -1; i = ne[i]){
        int j = e[i];
        if(st[j] == 0) dfs(j, l + 1);
    }
}

int lca(int u, int v, int step1, int step2){
    if(u == v) return step1 * 2 + step2;
    if(u < v) return lca(u, p[v], step1, step2 + 1); // 根据序号大小来爬树
    return lca(p[u], v, step1 + 1, step2);
}

int main(){
    memset(h, -1, sizeof h);
    
    cin >> n;
    
    for(int i = 0; i < n - 1; i ++){
        int a, b;
        cin >> a >> b;
        
        add(a, b);
        
        p[b] = a;
    }
    
    dfs(1, 1);
    
    cout << d << endl << w << endl;
    
    int u, v;
    cin >> u >> v;
    
    cout << lca(u, v, 0, 0);
    
    return 0;
}