节点间通路。给定有向图，设计一个算法，找出两个节点之间是否存在一条路径。
示例1:
输入：n = 3, graph = [[0, 1], [0, 2], [1, 2], [1, 2]], start = 0, target = 2 输出：true
示例2:
输入：n = 5, graph = [[0, 1], [0, 2], [0, 4], [0, 4], [0, 1], [1, 3], [1, 4], [1, 3], [2, 3], [3, 4]], start = 0, target = 4 输出 true
1.2点之间存在路径的dfs，这里的建图方式值得思考
class Solution: def findWhetherExistsPath(self, n: int, graph: List[List[int]], start: int, target: int) -> bool: g=collections.defaultdict(set) for k,v in graph: g[k].add(v) visited=set([start]) def dfs(i): if i==target:return True for j in g[i]: if j not in visited: visited.add(j) if dfs(j):return True return False return dfs(start)
