PAT A1094 The Largest Generation 人数最多的一代[树的遍历深度优先+计数]

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.

族层次结构通常由系谱树表示，同一层次上的所有节点都属于同一代。你的任务是找到人口最多的一代人

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.

每一个测试样例一开始是两个正整数 N(<100)：分别代表家族成员总数（家庭成员编号从01-N） M(<N)：家族成员中有孩子的人的数量

其后有M行，每一行包含了一个家庭成员的信息，格式如下：

ID K ID【1】ID【2】。。。ID【k】

ID是一个两位数代表了一个家庭成员，K是他孩子的数量，其后跟着K个他孩子们的ＩＤ。为简单起见，将根节点ID固定为01

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.

输出最多的人数以及相应的那一代的层次。假设那一代是独一无二的，根节点层次设为1

思路：建树-遍历树。通过遍历树记录每一层结点数。最后通过比较得到最大值以及所在层

#include<cstdio>
#include<vector>
using namespace std;
const int maxn = 110;
vector<int> NODE[maxn];//树的静态写法
int hashTable[maxn]={0};//记录每一层结点数

void DFS(int index,int level){
	hashTable[level]++;
	for(int j=0;j<NODE[index].size();j++){
		DFS(NODE[index][j],level+1);
	}
} 

int main(){
	int n,m,parent,k,child;
	scanf("%d%d",&n,&m);
	//------建树---------- 
	for(int i=0;i<m;i++){
		scanf("%d%d",&parent,&k);
		for(int j=0;j<k;j++){
			scanf("%d",&child);
			NODE[parent].push_back(child);
		}
	}
	DFS(1,1);
	//-----寻找最大值----- 
	int maxLevel=-1,maxValue=0;
	for(int i=1;i<maxn;i++){
		if(hashTable[i]>maxValue){
			maxValue=hashTable[i];
			maxLevel = i;
		}
	}
	//------输出--------- 
	printf("%d %d\n",maxValue,maxLevel);
	return 0;
}