浙大PAT (Advanced Level) Practise 1004. Counting Leaves (30)

#include <iostream>
#include <cstdio>
#include <map>
#include <vector>
using namespace std;
/*采用深度搜索方法，获取每一层的叶子节点，
用map存储数据，省去了建立树的麻烦，此方法更为简便*/
void dfs(map<int, vector<int> > &tree, map<int,int> &res, int id, int level)
{
if(tree.count(id) == 0){//如果没有子节点，相应的叶子节点+1
++res[level];
return;
}

for(int i = 0; i < tree[id].size(); ++i){//循环访问每一个子树
dfs(tree, res, tree[id][i], level+1);
}
}

int main()
{
int n,m;
map<int, vector<int> > tree;//用map按照结点与其子节点存取树
map<int, int> res;
scanf("%d %d",&n,&m);
for(int i = 0; i < m; ++i){//读取数据
int id, k;
scanf("%d %d", &id, &k);
while(k-- > 0){
int tmp;
scanf("%d",&tmp);
tree[id].push_back(tmp);
}
}

dfs(tree, res, 1, 1);//深度搜索获得结果
map<int,int>::iterator it = --res.end();
int maxLevel = (--res.end())->first;//获取最大层数
for(int i = 1; i <= maxLevel; ++i){//输出结果
if(i == 1){
cout<<res[i];
}
else{
cout<<" "<<res[i];
}
}
return 0;
}