ให้ N-ary tree หาจำนวนโหนดใบ (leaf nodes) ใน subtree ของทุกโหนด
ตัวอย่าง:
Input: N = 8, tree = [[2,3], [], [4,5,6], [7,8], [], [], [], []] Output: 1->5 2->1 3->4 4->2 5->1 6->1 7->1 8->1
อัลกอริทึม
- สร้าง tree adjacency list
- DFS จากโหนด 1
- leaf[node] = 0, visited[node] = 1
- วนลูปลูก: ถ้ายังไม่ visited DFS(l) แล้ว leaf[node] += leaf[l]
- ถ้าไม่มีลูก leaf[node] = 1
- พิมพ์ leaf ของทุกโหนด
การเขียนโปรแกรม C++
#include <bits/stdc++.h> using namespace std; void insertNode(int x, int y, vector<int> tree[]) { tree[x].push_back(y); } void DFS(int node, int leaf[], int visited[], vector<int> tree[]) { leaf[node] = 0; visited[node] = 1; for (auto it : tree[node]) { if (!visited[it]) { DFS(it, leaf, visited, tree); leaf[node] += leaf[it]; } } if (!tree[node].size()) leaf[node] = 1; } int main() { int N = 8; vector<int> tree[N + 1]; insertNode(1, 2, tree); insertNode(1, 3, tree); insertNode(3, 4, tree); insertNode(3, 5, tree); insertNode(3, 6, tree); insertNode(4, 7, tree); insertNode(4, 8, tree); int leaf[N + 1]; int visited[N + 1]; for (int i = 0; i <= N; i++) visited[i] = 0; DFS(1, leaf, visited, tree); for (int i = 1; i <= N; i++) cout << i << "->" << leaf[i] << endl; return 0; }
ผลลัพธ์
1->5 2->1 3->4 4->2 5->1 6->1 7->1 8->1
