[Leetcode/Graph, Depth-First Search(DFS)] 2359. Find Closest Node to Given Two Nodes

class Solution:
    def closestMeetingNode(self, edges: List[int], node1: int, node2: int) -> int:
        def trace_path(start):
            dist = {}
            step = 0
            while start != -1 and start not in dist:
                dist[start] = step
                step += 1
                start = edges[start]
            return dist

        dist1 = trace_path(node1)
        dist2 = trace_path(node2)

        result = -1
        min_dist = float('inf')

        for node in range(len(edges)):
            if node in dist1 and node in dist2:
                max_dist = max(dist1[node], dist2[node])
                if max_dist < min_dist:
                    min_dist = max_dist
                    result = node
        return result

 

• float('inf'): positive infinity
  • a special floating-point value that’s larger than any real number.
• step += 1
  • In the line step += 1, the variable step is keeping track of the number of steps (or distance) taken from the starting node to reach each subsequent node.