问题描述
当我尝试使用图形时,我正在dfs_recursion()
中学习图形
for(const ele of adjacencyList[v]){
if(!obj[ele]) return helper(ele);
}
代替
adjacencyList[v].forEach(neighbor => {
if(!obj[neighbor]){
return helper(neighbor);
}
})
为什么结果(graphTraversal.dfs_recursion("A")
)不同?
第一个是[ 'A','B','D','E','C' ]
第二个是[ 'A','C','F' ]
(正确答案)。
我在Internet上搜索了for...of
和forEach()
之间的区别,但仍然没有明白这一点。有人可以向我解释吗?
我的原始代码如下:
// Build an undirected graph
class Graph {
constructor(){
this.adjacencyList = {};
}
addVertex(vtx) {
if(!this.adjacencyList[vtx]) this.adjacencyList[vtx] = [];
return this.adjacencyList;
}
addEdge(v1,v2){
if(!(this.adjacencyList.hasOwnProperty(v1) && this.adjacencyList.hasOwnProperty(v2))) return "sorry but there is no vertex";
else{
this.adjacencyList[v1].push(v2);
this.adjacencyList[v2].push(v1);
}
}
dfs_recursion(vtx){
const arr = [],obj = {};
const adjacencyList = this.adjacencyList;
const helper = (v) => {
if(!v) return null;
arr.push(v);
obj[v] = true;
adjacencyList[v].forEach(neighbor => {
if(!obj[neighbor]){
return helper(neighbor);
}
})
}
helper(vtx);
return arr;
}
}
let graphTraversal = new Graph();
graphTraversal.addVertex("A");
graphTraversal.addVertex("B");
graphTraversal.addVertex("C");
graphTraversal.addVertex("D");
graphTraversal.addVertex("E");
graphTraversal.addVertex("F");
graphTraversal.addEdge("A","B");
graphTraversal.addEdge("A","C");
graphTraversal.addEdge("B","D");
graphTraversal.addEdge("C","E");
graphTraversal.addEdge("D","F");
graphTraversal.addEdge("E","F");
console.log(graphTraversal.dfs_recursion("A"));
解决方法
您的for...of
循环没有给出正确的结果,因为 return
导致其过早脱离循环。您可以通过删除来修复它return
:
for(const ele of adjacencyList[v]){
if(!obj[ele]) helper(ele);
}
Mozilla Developer Network (MDN):的解释
在
for...of
循环中,突然的迭代终止可以 由break
,throw
或return
引起。在这种情况下,迭代器为 关闭。(来源:
for...of
文章,“关闭迭代器”部分)