Leetcode 797. All Paths From Source to Target
阿新 • • 發佈:2018-08-16
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題目鏈接:https://leetcode.com/problems/all-paths-from-source-to-target/description/
Given a directed, acyclic graph of
N
nodes. Find all possible paths from node0
to nodeN-1
, and return them in any order.The graph is given as follows: the nodes are 0, 1, ..., graph.length - 1. graph[i] is a list of all nodes j for which the edge (i, j) exists.
Example: Input: [[1,2], [3], [3], []] Output: [[0,1,3],[0,2,3]] Explanation: The graph looks like this: 0--->1 | | v v 2--->3 There are two paths: 0 -> 1 -> 3 and 0 -> 2 -> 3.Note:
- The number of nodes in the graph will be in the range
[2, 15]
.- You can print different paths in any order, but you should keep the order of nodes inside one path.
看完題目描述,直覺就是DFS搜索解空間樹。因為不是二維表格所以不好用DP,同時是無環圖所以感覺比較像DFS。代碼如下:
class Solution(object): def allPathsSourceTarget(self, graph): """ :type graph: List[List[int]] :rtype: List[List[int]] """ res = [] target = len(graph) - 1 self.dfs([0], res, graph[0], graph, target)return res def dfs(self, curr_sol, res, curr_node, graph, target): if not curr_node: return for nxt in curr_node: if nxt == target: res.append(curr_sol + [nxt]) else: self.dfs(curr_sol+[nxt], res, graph[nxt], graph, target)
感覺是一道很標準的DFS,沒有什麽難點。
Leetcode 797. All Paths From Source to Target