pat甲級 1094 The Largest Generation (25 分)(dfs或者bfs）

題目鏈接：
傳送門

思路：直接dfs或者bfs記錄每層的節點數即可

代碼：
dfs:

#include <bits/stdc++.h>

using namespace std;

const int maxn = 105;

vector <int> g[maxn];
int h[maxn];
int mm;

void dfs(int u , int d) {
	h[d]++;
	mm = max(d , mm);
	for(int i = 0 ; i < g[u].size() ; i++) {
		int v = g[u][i];
		dfs(v , d + 1);
	}
}


int main() {
	int n , m;
	ios::sync_with_stdio(0);
	cin >> n >> m;
	for(int i = 0 ; i < m ; i++) {
		int id , k;
		cin >> id >> k;
		while(k--) {
			int t;
			cin >> t;
			g[id].push_back(t);
		}
	}
	mm = 0;
	dfs(1 , 1);
	int p = 1 , ans = 0;
	for(int i = 1 ; i <= mm ; i++) {
		if(ans < h[i]) {
			p = i;
			ans = h[i];
		}
	}
	cout << ans << " " << p << "\n";
	return 0;
}

bfs:

#include <bits/stdc++.h>

using namespace std;

const int maxn = 105;

vector <int> g[maxn];
int h[maxn] , level[maxn];

int main() {
	int n , m;
	ios::sync_with_stdio(0);
	cin >> n >> m;
	for(int i = 0 ; i < m ; i++) {
		int id , k;
		cin >> id >> k;
		while(k--) {
			int t;
			cin >> t;
			g[id].push_back(t);
		}
	}
	mm = 0;
	queue <int> q;
	level[1] = 1;
	q.push(1);
	while(!q.empty()) {
		int u = q.front(); q.pop();
		h[level[u]]++;
		for(int i = 0 ; i < g[u].size() ; i++) {
			int v = g[u][i];
			level[v] = level[u] + 1;
			q.push(v);
		}
	}
	int p = 1 , ans = 0;
	for(int i = 1 ; i <= n && h[i] ; i++) {
		if(ans < h[i]) {
			p = i;
			ans = h[i];
		}
	}
	cout << ans << " " << p << "\n";
	return 0;
}