2359. Find Closest Node to Given Two Nodes - Explanation

class Solution:
    def closestMeetingNode(self, edges: list[int], node1: int, node2: int) -> int:
        adj = defaultdict(list)
        for i, nei in enumerate(edges):
            adj[i].append(nei)

        def bfs(src, distMap):
            q = deque([(src, 0)])
            distMap[src] = 0
            while q:
                node, dist = q.popleft()
                for nei in adj[node]:
                    if nei not in distMap:
                        q.append((nei, dist + 1))
                        distMap[nei] = dist + 1

        node1Dist, node2Dist = {}, {}
        bfs(node1, node1Dist)
        bfs(node2, node2Dist)

        res, resDist = -1, float("inf")
        for i in range(len(edges)):
            if i in node1Dist and i in node2Dist:
                dist = max(node1Dist[i], node2Dist[i])
                if dist < resDist:
                    resDist, res = dist, i

        return res

class Solution:
    def closestMeetingNode(self, edges: list[int], node1: int, node2: int) -> int:
        n = len(edges)

        def bfs(src):
            dist = [-1] * n
            q = deque([src])
            dist[src] = 0

            while q:
                node = q.popleft()
                nei = edges[node]
                if nei == -1 or dist[nei] >= 0:
                    continue
                q.append(nei)
                dist[nei] = dist[node] + 1
            return dist

        node1Dist, node2Dist = bfs(node1), bfs(node2)

        res, resDist = -1, float("inf")
        for i in range(n):
            if node1Dist[i] != -1 and node2Dist[i] != -1:
                dist = max(node1Dist[i], node2Dist[i])
                if dist < resDist:
                    resDist, res = dist, i

        return res

class Solution:
    def closestMeetingNode(self, edges: List[int], node1: int, node2: int) -> int:
        n = len(edges)

        def dfs(node, dist):
            nei = edges[node]
            if nei != -1 and dist[nei] == -1:
                dist[nei] = dist[node] + 1
                dfs(nei, dist)

        node1Dist = [-1] * n
        node2Dist = [-1] * n
        node1Dist[node1] = node2Dist[node2] = 0

        dfs(node1, node1Dist)
        dfs(node2, node2Dist)

        res, resDist = -1, float("inf")
        for i in range(n):
            if min(node1Dist[i], node2Dist[i]) != -1:
                dist = max(node1Dist[i], node2Dist[i])
                if dist < resDist:
                    resDist, res = dist, i

        return res

class Solution:
    def closestMeetingNode(self, edges: list[int], node1: int, node2: int) -> int:
        n = len(edges)

        def dfs(node):
            dist = [-1] * n
            dist[node] = 0
            while edges[node] != -1 and dist[edges[node]] == -1:
                nei = edges[node]
                dist[nei] = dist[node] + 1
                node = nei
            return dist


        node1Dist, node2Dist = dfs(node1), dfs(node2)
        res, resDist = -1, float("inf")
        for i in range(n):
            if min(node1Dist[i], node2Dist[i]) != -1:
                dist = max(node1Dist[i], node2Dist[i])
                if dist < resDist:
                    resDist, res = dist, i
        return res