【PAT Advanced Level】1004. Counting Leaves (30)

利用广度优先搜索，找出每层的叶子节点的个数。

#include <iostream>#include <vector>#include <queue>#include <fstream>using namespace std;vector<vector<int>> tree;vector<int> ans;void BFS(int s){queue<pair<int, int>> q;q.push(make_pair(s, 0));int cur_step = 0;int cnt = 0;while (!q.empty()){int id = q.front().first;int step = q.front().second;q.pop();if(step > cur_step){cur_step = step;ans.push_back(cnt);cnt = 0;}if(tree[id].size() == 0) cnt++;for(int i = 0; i < tree[id].size(); i++)q.push(make_pair(tree[id][i], step + 1));}ans.push_back(cnt);return;}int main(){//fstream cin("a.txt");int N, M;cin>>N>>M;tree.resize(N + 1);for(int i = 0; i < M; i++){int id, num;cin>>id>>num;while (num--){int tmp;cin>>tmp;tree[id].push_back(tmp);}}BFS(1);for(int i = 0; i < ans.size(); i++){if(i == 0)cout<<ans[i];elsecout<<" "<<ans[i];}cout<<endl;}