Articulation Points

# Finding Articulation Points in Undirected Graph
def computeAP(l):  # noqa: E741
    n = len(l)
    outEdgeCount = 0
    low = [0] * n
    visited = [False] * n
    isArt = [False] * n

    def dfs(root, at, parent, outEdgeCount):
        if parent == root:
            outEdgeCount += 1
        visited[at] = True
        low[at] = at

        for to in l[at]:
            if to == parent:
                pass
            elif not visited[to]:
                outEdgeCount = dfs(root, to, at, outEdgeCount)
                low[at] = min(low[at], low[to])

                # AP found via bridge
                if at < low[to]:
                    isArt[at] = True
                # AP found via cycle
                if at == low[to]:
                    isArt[at] = True
            else:
                low[at] = min(low[at], to)
        return outEdgeCount

    for i in range(n):
        if not visited[i]:
            outEdgeCount = 0
            outEdgeCount = dfs(i, i, -1, outEdgeCount)
            isArt[i] = outEdgeCount > 1

    for x in range(len(isArt)):
        if isArt[x] is True:
            print(x)


# Adjacency list of graph
data = {
    0: [1, 2],
    1: [0, 2],
    2: [0, 1, 3, 5],
    3: [2, 4],
    4: [3],
    5: [2, 6, 8],
    6: [5, 7],
    7: [6, 8],
    8: [5, 7],
}
computeAP(data)
Algerlogo

Β© Alger 2022

About us

We are a group of programmers helping each other build new things, whether it be writing complex encryption programs, or simple ciphers. Our goal is to work together to document and model beautiful, helpful and interesting algorithms using code. We are an open-source community - anyone can contribute. We check each other's work, communicate and collaborate to solve problems. We strive to be welcoming, respectful, yet make sure that our code follows the latest programming guidelines.