diff --git a/problems/kamacoder/0109.冗余连接II.md b/problems/kamacoder/0109.冗余连接II.md index bd707bf6..2bd4eac6 100644 --- a/problems/kamacoder/0109.冗余连接II.md +++ b/problems/kamacoder/0109.冗余连接II.md @@ -351,6 +351,92 @@ public class Main { ``` ### Python +```python +from collections import defaultdict + +father = list() + + +def find(u): + if u == father[u]: + return u + else: + father[u] = find(father[u]) + return father[u] + + +def is_same(u, v): + u = find(u) + v = find(v) + return u == v + + +def join(u, v): + u = find(u) + v = find(v) + if u != v: + father[u] = v + + +def is_tree_after_remove_edge(edges, edge, n): + # 初始化并查集 + global father + father = [i for i in range(n + 1)] + + for i in range(len(edges)): + if i == edge: + continue + s, t = edges[i] + if is_same(s, t): # 成環,即不是有向樹 + return False + else: # 將s,t放入集合中 + join(s, t) + return True + + +def get_remove_edge(edges): + # 初始化并查集 + global father + father = [i for i in range(n + 1)] + + for s, t in edges: + if is_same(s, t): + print(s, t) + return + else: + join(s, t) + + +if __name__ == "__main__": + # 輸入 + n = int(input()) + edges = list() + in_degree = defaultdict(int) + + for i in range(n): + s, t = map(int, input().split()) + in_degree[t] += 1 + edges.append([s, t]) + + # 尋找入度為2的邊,並紀錄其下標(index) + vec = list() + for i in range(n - 1, -1, -1): + if in_degree[edges[i][1]] == 2: + vec.append(i) + + # 輸出 + if len(vec) > 0: + # 情況一:刪除輸出順序靠後的邊 + if is_tree_after_remove_edge(edges, vec[0], n): + print(edges[vec[0]][0], edges[vec[0]][1]) + # 情況二:只能刪除特定的邊 + else: + print(edges[vec[1]][0], edges[vec[1]][1]) + else: + # 情況三: 原圖有環 + get_remove_edge(edges) +``` + ### Go ### Rust