题目：
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
代码实现：
class Solution { public boolean findWhetherExistsPath(int n, int[][] graph, int start, int target) { Set<Integer>[] adjacentArr = new Set[n]; for (int i = 0; i < n; i++) { adjacentArr[i] = new HashSet<Integer>(); } for (int[] edge : graph) { if (edge[0] != edge[1]) { adjacentArr[edge[0]].add(edge[1]); } } boolean[] visited = new boolean[n]; visited[start] = true; Queue<Integer> queue = new ArrayDeque<Integer>(); queue.offer(start); while (!queue.isEmpty() && !visited[target]) { int vertex = queue.poll(); Set<Integer> adjacent = adjacentArr[vertex]; for (int next : adjacent) { if (!visited[next]) { visited[next] = true; queue.offer(next); } } } return visited[target]; }}
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