桥 - المسألة

#995. 桥

الإحصائيات

题目描述

给出一个 $n$ 个点，$m$ 条边的无向图，求图的桥。

输入格式

第一行输入两个正整数 $n, m$。

下面 $m$ 行每行输入两个正整数 $x,y$ 表示 $x$ 到 $y$ 有一条边。

输出格式

输出若干行，每行一条边，表示所有的桥边，按照输入的顺序进行输出，不能调换两端点的顺序。

图中可能含有重边与自环。

样例数据

样例 1 输入

样例 1 输出

5 6

样例 2 输入

样例 2 输出

1 6
6 7

子任务

对于全部数据，$1 \leq n \leq 10^5, 1 \leq x,y \leq n , 1 \leq m \leq 5 \times 10^5$.

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