《中英双解》leetCode Find if path exists in graph
作者:互联网
There is a bi-directional graph with
n
vertices, where each vertex is labeled from0
ton - 1
(inclusive). The edges in the graph are represented as a 2D integer arrayedges
, where eachedges[i] = [ui, vi]
denotes a bi-directional edge between vertexui
and vertexvi
. Every vertex pair is connected by at most one edge, and no vertex has an edge to itself.You want to determine if there is a valid path that exists from vertex
start
to vertexend
.Given
edges
and the integersn
,start
, andend
, returntrue
if there is a valid path fromstart
toend
, orfalse
otherwise.有一个具有 n个顶点的 双向 图,其中每个顶点标记从 0 到 n - 1(包含 0 和 n - 1)。图中的边用一个二维整数数组 edges 表示,其中 edges[i] = [ui, vi] 表示顶点 ui 和顶点 vi 之间的双向边。 每个顶点对由 最多一条 边连接,并且没有顶点存在与自身相连的边。
请你确定是否存在从顶点 start 开始,到顶点 end 结束的 有效路径 。
给你数组 edges 和整数 n、start和end,如果从 start 到 end 存在 有效路径 ,则返回 true,否则返回 false 。
来源:力扣(LeetCode)
链接:https://leetcode-cn.com/problems/find-if-path-exists-in-graph
著作权归领扣网络所有。商业转载请联系官方授权,非商业转载请注明出处。Example 1:
Input: n = 3, edges = [[0,1],[1,2],[2,0]], start = 0, end = 2 Output: true Explanation: There are two paths from vertex 0 to vertex 2: - 0 → 1 → 2 - 0 → 2Example 2:
Input: n = 6, edges = [[0,1],[0,2],[3,5],[5,4],[4,3]], start = 0, end = 5 Output: false Explanation: There is no path from vertex 0 to vertex 5.Constraints:
1 <= n <= 2 * 105
0 <= edges.length <= 2 * 105
edges[i].length == 2
0 <= ui, vi <= n - 1
ui != vi
0 <= start, end <= n - 1
- There are no duplicate edges.
- There are no self edges.
BFS
class Solution {
public boolean validPath(int n, int[][] edges, int start, int end) {
HashMap<Integer, List<Integer>> graph = new HashMap<Integer,List<Integer>>();
for (int i= 0;i <edges.length;i++)
{
if(graph.containsKey(edges[i][0]))
{
graph.get(edges[i][0]).add(edges[i][1]);
}
else
{
List<Integer> temp = new ArrayList<Integer>();
temp.add(edges[i][1]);
graph.put(edges[i][0],temp);
}
if(graph.containsKey(edges[i][1]))
{
graph.get(edges[i][1]).add(edges[i][0]);
}
else
{
List<Integer> temp2 = new ArrayList<Integer>();
temp2.add(edges[i][0]);
graph.put(edges[i][1],temp2);
}
}
int[] visited = new int[n];
Queue<Integer> queue = new LinkedList<Integer>();
queue.add(start);
visited[start] = 1;
while(!queue.isEmpty())
{
int top = queue.remove();
if(graph.containsKey(top))
{
for(int k=0;k < graph.get(top).size();k++)
{
if(visited[graph.get(top).get(k)] != 1)
{
queue.add(graph.get(top).get(k));
visited[graph.get(top).get(k)] = 1;
}
}
}
}
return visited[end] == 1;
}
}
DFS
class Solution {
public boolean validPath(int n, int[][] edges, int start, int end) {
boolean[] visited = new boolean[n + 1];
boolean newVisited = true;
visited[start] = true;
while(!visited[end] && newVisited){
newVisited = false;
for(int[] edge : edges){
if(visited[edge[0]] && !visited[edge[1]]){
visited[edge[1]] = true;
newVisited = true;
}
if(!visited[edge[0]] && visited[edge[1]]){
visited[edge[0]] = true;
newVisited = true;
}
}
}
return visited[end];
}
}
标签:end,双解,exists,int,graph,start,edges,visited 来源: https://blog.csdn.net/weixin_46272350/article/details/121595221