


PHP implementation of Kruskal algorithm example analysis, Kruskal algorithm example
The example in this article shows the implementation method of Kruscal algorithm (kruscal) implemented in PHP, and is shared with everyone for your reference. I believe it has certain reference value for everyone's PHP program design.
The specific code is as follows:
<?php require 'edge.php'; $a = array( 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i' ); $b = array( 'ab' => '10', 'af' => '11', 'gb' => '16', 'fg' => '17', 'bc' => '18', 'bi' => '12', 'ci' => '8', 'cd' => '22', 'di' => '21', 'dg' => '24', 'gh' => '19', 'dh' => '16', 'de' => '20', 'eh' => '7', 'fe' => '26' ); $test = new Edge($a, $b); print_r($test->kruscal()); ?>
edge.php file code is as follows:
<?php //边集数组的边类 class EdgeArc { private $begin; //起始点 private $end; //结束点 private $weight; //权值 public function EdgeArc($begin, $end, $weight) { $this->begin = $begin; $this->end = $end; $this->weight = $weight; } public function getBegin() { return $this->begin; } public function getEnd() { return $this->end; } public function getWeight() { return $this->weight; } } class Edge { //边集数组实现图 private $vexs; //顶点集合 private $arc; //边集合 private $arcData; //要构建图的边信息 private $krus; //kruscal算法时存放森林信息 public function Edge($vexsData, $arcData) { $this->vexs = $vexsData; $this->arcData = $arcData; $this->createArc(); } //创建边 private function createArc() { foreach ($this->arcData as $key => $value) { $key = str_split($key); $this->arc[] = new EdgeArc($key[0], $key[1], $value); } } //对边数组按权值排序 public function sortArc() { $this->quicklySort(0, count($this->arc) - 1, $this->arc); return $this->arc; } //采用快排 private function quicklySort($begin, $end, &$item) { if ($begin < 0($begin >= $end)) return; $key = $this->excuteSort($begin, $end, $item); $this->quicklySort(0, $key - 1, $item); $this->quicklySort($key + 1, $end, $item); } private function excuteSort($begin, $end, &$item) { $key = $item[$begin]; $left = array(); $right = array(); for ($i = ($begin + 1); $i <= $end; $i++) { if ($item[$i]->getWeight() <= $key->getWeight()) { $left[] = $item[$i]; } else { $right[] = $item[$i]; } } $return = $this->unio($left, $right, $key); $k = 0; for ($i = $begin; $i <= $end; $i++) { $item[$i] = $return[$k]; $k++; } return $begin + count($left); } private function unio($left, $right, $key) { return array_merge($left, array( $key ) , $right); } //kruscal算法 public function kruscal() { $this->krus = array(); $this->sortArc(); foreach ($this->vexs as $value) { $this->krus[$value] = "0"; } foreach ($this->arc as $key => $value) { $begin = $this->findRoot($value->getBegin()); $end = $this->findRoot($value->getEnd()); if ($begin != $end) { $this->krus[$begin] = $end; echo $value->getBegin() . "-" . $value->getEnd() . ":" . $value->getWeight() . "\n"; } } } //查找子树的尾结点 private function findRoot($node) { while ($this->krus[$node] != "0") { $node = $this->krus[$node]; } return $node; } } ?>
Interested readers can debug and run the Kruskal algorithm example in this article. I believe there will be new gains.
Are you sure you want to use adjacency list? Because in Kruskal's algorithm only edges and costs need to be stored, using adjacency lists makes little sense and is not easy to sort. It’s best to combine it with specific topics. I have a topic here, which has a complete code. Just understand it slowly.blog.csdn.net/...751786
The following is the Kruskal algorithm implemented by union lookup, which solves the minimum cost of generating the network and outputs the path in the generated network.
#include
#include
using namespace std;
int p[1001],rank[1001];
int cho[1001];
struct edge
{
int u,v,w;//u represents the starting point number, v represents the end point number, w represents the cost of the path
}e[15001];
int n,m; //n represents the number of points, m represents the number of paths
void Init()
{
int i;
for(i=1;i {
p[i]=i;
rank[i]=0;
}
}
bool cmp(edge a,edge b)
{
return a. w
int Find(int t)
{
if(p[t]!=t)
{
p[t]=Find(p[ t]);
}
return p[t];
}
int Union(int a,int b)
{
int x,y;
x= Find(a);
y=Find(b);
if(rank[x]>rank[y])
{
p[y]=x;
}
else
{
p[x]=y;
if(rank[x]==rank[y])
rank[y]++;
}
return 0;
}
int main()
{
scanf("%d%d",&n,&m);
int i,j;
for(i= 0;i
scanf("%d%d%d",&e[i].u,&e[i].v,&e[i].w);
}
Init();
sort(e,e+m,cmp);
int cnt=0,ans=0;
for(i=0;i
if(Find(e[i].u)!=Find(e[i].v))
{
cnt++;
ans+=e[i].w ;
Union(e[i].u,e[i].v);
cho[++cho[0]]=i;
if(cnt==n-1)
break;
}
}
printf("%d\n",ans);
for(j=1;j {
printf("%d %d\n",e[cho[j]].u,e[cho[j]].v);
}
return 0;
}.. .The rest of the full text>>
There are many more in it. If you are interested, you can read it. Look

php把负数转为正整数的方法:1、使用abs()函数将负数转为正数,使用intval()函数对正数取整,转为正整数,语法“intval(abs($number))”;2、利用“~”位运算符将负数取反加一,语法“~$number + 1”。

实现方法:1、使用“sleep(延迟秒数)”语句,可延迟执行函数若干秒;2、使用“time_nanosleep(延迟秒数,延迟纳秒数)”语句,可延迟执行函数若干秒和纳秒;3、使用“time_sleep_until(time()+7)”语句。

php字符串有下标。在PHP中,下标不仅可以应用于数组和对象,还可应用于字符串,利用字符串的下标和中括号“[]”可以访问指定索引位置的字符,并对该字符进行读写,语法“字符串名[下标值]”;字符串的下标值(索引值)只能是整数类型,起始值为0。

php除以100保留两位小数的方法:1、利用“/”运算符进行除法运算,语法“数值 / 100”;2、使用“number_format(除法结果, 2)”或“sprintf("%.2f",除法结果)”语句进行四舍五入的处理值,并保留两位小数。

判断方法:1、使用“strtotime("年-月-日")”语句将给定的年月日转换为时间戳格式;2、用“date("z",时间戳)+1”语句计算指定时间戳是一年的第几天。date()返回的天数是从0开始计算的,因此真实天数需要在此基础上加1。

在php中,可以使用substr()函数来读取字符串后几个字符,只需要将该函数的第二个参数设置为负值,第三个参数省略即可;语法为“substr(字符串,-n)”,表示读取从字符串结尾处向前数第n个字符开始,直到字符串结尾的全部字符。

方法:1、用“str_replace(" ","其他字符",$str)”语句,可将nbsp符替换为其他字符;2、用“preg_replace("/(\s|\ \;||\xc2\xa0)/","其他字符",$str)”语句。

查找方法:1、用strpos(),语法“strpos("字符串值","查找子串")+1”;2、用stripos(),语法“strpos("字符串值","查找子串")+1”。因为字符串是从0开始计数的,因此两个函数获取的位置需要进行加1处理。


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