DepthFirstSearch [深度优先搜索]

# 介绍

深度优先搜索算法（英语：Depth-First-Search，DFS）是一种用于遍历或搜索树或图的算法。这个算法会尽可能深地搜索树的分支。当节点 v 的所在边都己被探寻过，搜索将回溯到发现节点 v 的那条边的起始节点。这一过程一直进行到已发现从源节点可达的所有节点为止。如果还存在未被发现的节点，则选择其中一个作为源节点并重复以上过程，整个进程反复进行直到所有节点都被访问为止。这种算法不会根据图的结构等信息调整执行策略。

# 演示

# 实现

# JavaScript

迭代法：

class GraphUnweightedUndirected {
  // Unweighted Undirected Graph class
  constructor () {
    this.connections = {}
  }

  addNode (node) {
    // Function to add a node to the graph (connection represented by set)
    this.connections[node] = new Set()
  }

  addEdge (node1, node2) {
    // Function to add an edge (adds the node too if they are not present in the graph)
    if (!(node1 in this.connections)) { this.addNode(node1) }
    if (!(node2 in this.connections)) { this.addNode(node2) }
    this.connections[node1].add(node2)
    this.connections[node2].add(node1)
  }

  DFSIterative (node, value) {
    // DFS Function to search if a node with the given value is present in the graph
    const stack = [node]
    const visited = new Set()
    while (stack.length > 0) {
      const currNode = stack.pop()
      // if the current node contains the value being searched for, true is returned
      if (currNode === value) { return true }
      // adding the current node to the visited set
      visited.add(currNode)
      // adding neighbours in the stack
      for (const neighbour of this.connections[currNode]) {
        if (!visited.has(neighbour)) {
          stack.push(neighbour)
        }
      }
    }
    return false
  }
}

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递归法：

class GraphUnweightedUndirected {
  // Unweighted Undirected Graph class
  constructor () {
    this.connections = {}
  }

  addNode (node) {
    // Function to add a node to the graph (connection represented by set)
    this.connections[node] = new Set()
  }

  addEdge (node1, node2) {
    // Function to add an edge (adds the node too if they are not present in the graph)
    if (!(node1 in this.connections)) { this.addNode(node1) }
    if (!(node2 in this.connections)) { this.addNode(node2) }
    this.connections[node1].add(node2)
    this.connections[node2].add(node1)
  }

  DFSRecursive (node, value, visited = new Set()) {
    // DFS Function to search if a node with the given value is present in the graph
    // checking if the searching node has been found
    if (node === value) { return true }
    // adding the current node to the visited set
    visited.add(node)
    // calling the helper function recursively for all unvisited nodes
    for (const neighbour of this.connections[node]) {
      if (!visited.has(neighbour)) {
        if (this.DFSRecursive(neighbour, value, visited)) { return true }
      }
    }
    return false
  }
}

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# 参考

编辑

上次更新: 2022/10/18, 09:41:50

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