1094 The Largest Generation (25 point(s))

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本篇博客介绍了一道编程题的解决方案，题目要求找出一个家族树中人口最多的一代。通过深度优先搜索（DFS）算法遍历树结构，统计每一代的人口数量，最终确定并输出人口最多的那一代及其人口数。

1094 The Largest Generation (25 point(s))

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

树的遍历。参考1004。

考点：DFS

易错点：maxLevel初始化为1，否则当只有一个根节点时没有输出（case#1出现WA，23分）。

#include<iostream>
#include<cstring>
#include<vector>
#include<queue>
using namespace std;
const int MAX = 107;
vector<int> graph[MAX];
int level[MAX]={0};
int cnt[MAX]={0};
int maxLevel = 1;//最少是1 
void dfs(int v){
	cnt[level[v]]++;
	for(int i=0;i<graph[v].size();i++){
		int cur = graph[v][i];
		level[cur]=level[v]+1;
		maxLevel = max(maxLevel,level[cur]);
		dfs(cur);
	}
}
int main(void){
	int N,M;cin>>N>>M;
	int id,k,a;
	while(M--){
		cin>>id>>k;
		while(k--){
			cin>>a;
			graph[id].push_back(a);
		}
	}
	int root = 1;level[root]=1;
	dfs(root);
	int max = 0;int generation; 
	for(int i=1;i<=maxLevel;i++){
		if(cnt[i]>max){
			max = cnt[i];
			generation = i;
		}
	}
	cout<<max<<" "<<generation<<endl;
	return 0;
}

看看别人更简洁的代码！使用迭代器！