PHP常用算法整理

1.排序-冒泡
function mp($arr = []){
    $len = count($arr);
    if($len == 0) return [];
    if($len == 1) return $arr;

　　　//第一层控制冒泡轮数 $len-1轮
    for($i=1;$i<$len;$i++){
　　　　　//相邻两个比较，交换位置 每个for结束最大的都排到最后for循环-1  比较次数len-$i
        for($j=0;$j<$len - $i;$j++){
            if($arr[$j] > $arr[$j+1]){
                $temp = $arr[$j];
                $arr[$j] = $arr[$j+1];
                $arr[$j+1] = $temp;
            }
        }
    }
    return $arr;
}
2.排序-快排

function quickly_order($arr=[]){
    if(count($arr) == 0 || !is_array($arr)){
        return [];
    }
    if(count($arr) == 1){
        return $arr;
    }

    $mid = $arr[0];
    $left = $right = [];
    foreach($arr as $val){
        if($val > $mid){
            $right[] = $val;
        }elseif($val < $mid){
            $left[] = $val;
        }
    }

    $left = quickly_order($left);
    $right = quickly_order($right);

    return array_merge($left,[$mid],$right);
}
3.usort()排序

function order_array($arr = []){
    if(count($arr) == 0) return [];

    usort($arr,function ($a,$b){
        return $a == $b ? 0:($a>$b ? 1:-1);
    });

    return $arr;
}
4.二叉树遍历
  建立如下二叉树

 

class Node{
    public $data=null;
    public $left=null;
    public $right=null;
}

$node1 = new Node();
$node2 = new Node();
$node3 = new Node();
$node4 = new Node();
$node5 = new Node();
$node6 = new Node();
$node7 = new Node();
$node8 = new Node();
$node9 = new Node();

$node1->data = 1;
$node2->data = 2;
$node3->data = 3;
$node4->data = 4;
$node5->data = 5;
$node6->data = 6;
$node7->data = 7;
$node8->data = 8;
$node9->data = 9;

$node1->left = $node2;
$node1->right = $node3;
$node2->left = $node4;
$node2->right = $node5;
$node3->left = $node6;
$node3->right = $node7;
$node4->left = $node8;
$node4->right = $node9;

//深度优先

function binary_tree($node){
    $return = [];  //返回
    $data = [];    
    array_push($data,$node);  //入栈
    while(count($data) > 0){
        $_node = array_pop($data); //尾出
        $return[] = $_node->data;

　　　　　//先进后出 先把右边节点入栈
        if(!empty($_node->right)){
            array_push($data,$_node->right);
        }

        if(!empty($_node->left)){
            array_push($data,$_node->left);
        }
    }

    return $return;
}

echo "<pre>";
print_r(binary_tree($node1));
运行结果：

//广度优先

function binary_tree2($node){
    $return = [];   //返回
    $data = [];
    array_push($data,$node);    //入栈
    while(count($data) > 0){
        $_node = array_shift($data); //首出
        $return[] = $_node->data;

　　　　　//先进先出 左先进
        if(!empty($_node->left)){
            array_push($data,$_node->left);
        }

        if(!empty($_node->right)){
            array_push($data,$_node->right);
        }
    }

    return $return;
}

echo "<pre>";
print_r(binary_tree2($node1));
运行结果：

 

 

 5.全排列

function sort_full($arr,$str="",&$return=[]){
    if(count($arr) == 0 || !is_array($arr)) return [];

    if(count($arr) == 1){
        $return[] = $str.$arr[0];
    }else{
        for($i=0;$i<count($arr);$i++){
            $temp = $arr[0];
            $arr[0] = $arr[$i];
            $arr[$i] = $temp;
            sort_full(array_slice($arr,1),$str.$arr[0],$return);
        }
    }

    return $return;
}

echo "<pre>";
print_r(sort_full(['a','b','c','d']));
运行结果：