【PAT甲级】1094 The Largest Generation（25 分）（dfs/bfs）

题目链接

A family hierarchy is usually presented by a pedigree tree where all the nodes on the same level belong to the same generation. Your task is to find the generation with the largest population.

Input Specification:

Each input file contains one test case. Each case starts with two positive integers N (<100) which is the total number of family members in the tree (and hence assume that all the members are numbered from 01 to N), and M (<N) which is the number of family members who have children. Then M lines follow, each contains the information of a family member in the following format:

ID K ID[1] ID[2] ... ID[K]

where ID is a two-digit number representing a family member, K (>0) is the number of his/her children, followed by a sequence of two-digit ID's of his/her children. For the sake of simplicity, let us fix the root ID to be 01. All the numbers in a line are separated by a space.

Output Specification:

For each test case, print in one line the largest population number and the level of the corresponding generation. It is assumed that such a generation is unique, and the root level is defined to be 1.

Sample Input:

23 13
21 1 23
01 4 03 02 04 05
03 3 06 07 08
06 2 12 13
13 1 21
08 2 15 16
02 2 09 10
11 2 19 20
17 1 22
05 1 11
07 1 14
09 1 17
10 1 18

Sample Output:

9 4

题意：求树中哪一层的孩子节点最多，输出孩子节点个数和这一层的深度。

思路：dfs或bfs

代码：

#include <bits/stdc++.h>
using namespace std;
#define rep(i,a,n) for(int i=a;i<n;i++)
#define drep(i,n,a) for(int i=n;i>=a;i--)
#define mem(a,n) memset(a,n,sizeof(a))
#define lowbit(i) ((i)&(-i))
typedef long long ll;
typedef unsigned long long ull;
const ll INF=0x3f3f3f3f;
const double eps = 1e-6;
const int N = 1e2+5;

int cnt[N],depth[N];
vector<vector<int> >g;
/**dfs */
void dfs(int root,int dep){
    cnt[dep]++;
    for(auto child:g[root])
        dfs(child,dep+1);
}
int main(){
    int n,m,id,k;
    scanf("%d%d",&n,&m);
    g.resize(n+1);
    for(int i=0;i<m;i++){
        scanf("%d%d",&id,&k);
        for(int j=0;j<k;j++){
            int x;
            scanf("%d",&x);
            g[id].push_back(x);
        }
    }
    int root=1;
    dfs(root,1);
    /**   ///bfs
    queue<int>que;
    que.push(root);
    depth[root]=1;
    while(!que.empty()){
        root=que.front();
        que.pop();
        cnt[depth[root]]++;
        for(auto child: g[root]){
            depth[child]=depth[root]+1;
            que.push(child);
        }
    }
    **/
    int maxSum=0,ansDepth;
    for(int i=0;i<=100;i++){
        if(maxSum<cnt[i]){
            maxSum=cnt[i];
            ansDepth=i;
        }
    }
    printf("%d %d", maxSum,ansDepth);
    return 0;
}