使用Lua的BFS算法可找到2个节点之间的最短路径 [英] BFS algorithm using Lua that finds the shortest path between 2 nodes
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问题描述
我设法编写了一个代码,该代码使用BFS算法遍历所有图形节点.这是容易的部分:)
I managed to write a code, that iterates over all graph nodes using the BFS algorithm. It was the easy part :)
不,我坚持要获得两个节点之间的最短路径.
No I am stuck with getting the shortest path between two nodes.
到目前为止,这是我的代码:
This is my code so far:
function table.contains(table, element)
for _, value in pairs(table) do
if value == element then
return true
end
end
return false
end
queue = {stack={}}
function queue:en(e)
table.insert(self.stack, e)
end
function queue:de()
local e = self.stack[1]
self.stack[1] = nil
local new_stack = {}
for _, v in pairs(self.stack) do
table.insert(new_stack, v)
end
self.stack = new_stack
return e
end
function queue:count()
return #self.stack
end
function bfs()
start = 1
goal = 10
visited = {}
path = {}
graph = {}
graph[1] = {2,3,4}
graph[2] = {6,5,1}
graph[3] = {1}
graph[4] = {7,8}
graph[5] = {9,10,2}
graph[6] = {2}
graph[7] = {4,11,12}
graph[8] = {4}
graph[9] = {5}
graph[10] = {5}
graph[11] = {7}
graph[12] = {7}
queue:en(start)
table.insert(visited, start)
depth = 1
while queue:count() > 0 do
node = queue:de()
for _, exit in pairs(graph[node]) do
if not table.contains(visited, exit) then
table.insert(visited, exit)
if exit == goal then
print("GOAL : " .. exit)
do return end
end
if graph[exit] then
print("Node: " .. exit .. ", Depth: " .. depth)
queue:en(exit)
end
end
end
depth = depth + 1
end
end
bfs()
它生成的此输出:
Node: 2, Depth: 1
Node: 3, Depth: 1
Node: 4, Depth: 1
Node: 6, Depth: 2
Node: 5, Depth: 2
Node: 7, Depth: 4
Node: 8, Depth: 4
Node: 9, Depth: 6
GOAL : 10
在当前示例中,我需要获得从1到10的最短路径.
With the current example I would need to get the shortest path from 1 to 10.
推荐答案
这是可以完成的方法.
queue.lua
local queue = {}
function queue:init()
local q = {}
q.stack = {}
function q:push(e)
table.insert(self.stack, e)
end
function q:pull()
local e = self.stack[1]
table.remove(self.stack, 1)
return e
end
function q:count()
return #self.stack
end
return q
end
return queue
tbl.lua
function table.contains(tbl, e)
for _, v in pairs(tbl) do
if v == e then
return true
end
end
return false
end
function table.copy(tbl)
local t = {}
for _, v in pairs(tbl) do
table.insert(t, v)
end
return t
end
bfs.lua
require "tbl" -- table.contains and table.copy
queue = require "queue"
local function bfs(graph, start, goal)
if not graph[start] then
return false
end
local visited = {}
local queue = queue:init()
queue:push({start})
table.insert(visited, start)
while queue:count() > 0 do
local path = queue:pull()
local node = path[#path]
if node == goal then return path end
for _, exit in pairs(graph[node]) do
if not table.contains(visited, exit) then
table.insert(visited, exit)
if graph[exit] then
local new = table.copy(path)
table.insert(new, exit)
queue:push(new)
end
end
end
end
return false
end
return bfs
用法:
将所有三个文件保存到lua路径.
Save all three files to your lua path.
bfs =需要"bfs"
bfs = require "bfs"
路径= bfs(结束,开始,目标)
path = bfs(grap, start, goal)
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