Graph: 0−1, 1−2, 0−2, 1−3. Start DFS at 0. Visit 0: disc[0]=0, low[0]=0. Visit 1: disc[1]=1, low[1]=1. Visit 2: disc[2]=2, low[2]=2. Back edge 2−0: low[2]=min(2,0)=0. Backtrack to 1: low[1]=min(1,0)=0.
Visit 3: disc[3]=3, low[3]=3. Backtrack to 1: check low[3]=3 > disc[1]=1, so edge 1−3 is a bridge. Final bridges: {1−3}. All other edges are part of the cycle 0−1−2−0.