php基本的排序查找

//二分查找（数组里查找某个元素）
function bin_sch($arr,$low,$high,$k ){
    
    if ($low <= $high){
        $mid = floor(($low+$high)/2);
        if ($array[$mid] == $k){
            return $mid;
        }elseif ($k < $array[$mid]){
            return bin_sch($array, $low, $mid-1, $k);
        }else{
            return bin_sch($array, $mid+1, $high, $k);
        }
    }
return false;
} 


<?php
$data = array(4,6,7,8,14,55,67,145,218,237,284);

$num = binarysearch(4);
var_dump($num);
function binarysearch($num){
	global $data;
	$count = count($data);
	$high = $count-1;
	$low = 0;
	
	while ($high >= $low){
		$mid  = floor(($high+$low)/2);
		if($num == $data[$mid]){
			return $mid;
		}elseif($num > $data[$mid]){
			$low = $mid + 1;
		}elseif($num < $data[$mid]){
			$high = $mid - 1;
		}
	}
	return false;
}

//顺序查找（数组里查找某个元素）
$data = array(14,6,7,8,4,55,67,45,118,37,84);

var_dump(search(45));

function search($num){
	global $data;
	$position = false;
	for ($i=0,$count=count($data); $i < $count; $i++) { 
		if($data[$i] == $num){
			$position = $i;
			break;
		}
	}
	return $position;
}

//线性表的删除（数组中实现）
function delete_array_element($array, $i)
{
$len = count($array);
for ($j=$i; $j<$len; $j++){
$array[$j] = $array[$j+1];
}
array_pop($array);
return $array;
} 

//冒泡排序（数组排序）
function bubble_sort($array)
{
    $count = count($array);
    if ($count <= 0) return false;
        for($i=0; $i<$count; $i++){
            for($j=0;$j<$count-$i;$j++){
                if ($array[$j] < $array[$j-1]){
                    $tmp = $array[$j];
                    $array[$j] = $array[$j-1];
                    $array[$j-1] = $tmp;
                }
            }
        }
return $array;
} 

//快速排序（数组排序）
function quicksort($array) {
    if (count($array) <= 1) return $array;  //递归的终止条件
        $key = $array[0];   //选取标准
        $left_arr = array();
        $right_arr = array();
        for ($i=1; $i<count($array); $i++){
            if ($array[$i] <= $key)   //进行循环比较，大的放一组，小的放一组
                $left_arr[] = $array[$i];
            else
                $right_arr[] = $array[$i];
        }
    $left_arr = quicksort($left_arr);    //对小的进行递归操作
    $right_arr = quicksort($right_arr);  //对大的进行递归操作
    return array_merge($left_arr, array($key), $right_arr);    //合并数组
} 

//简单选择排序
function selectSort($arr){
	$len = count($arr);
	for($i = 0;$i<$len;$i++){
		$min = $i;
		for($j=$i+1;$j<=$len-1;$j++){
			if($arr[$min]>$arr[$j]){
				$min = $j;
			}
		}
 
		if($min != $i){
			$tmp = $arr[$i];
			$arr[$i] = $arr[$min];
			$arr[$min] = $tmp;
		}
	}
 
	return $arr;
}
 
echo "<pre>";
var_dump(selectSort($arr));

//直接插入排序
    function insert_sort($arr){     
        $count = count($arr);     
        for($i=1; $i<$count; $i++){     
            $tmp = $arr[$i];     
            $j = $i - 1;     
            while($arr[$j] > $tmp){     //核心
                $arr[$j+1] = $arr[$j];     
                $arr[$j] = $tmp;     
                $j--;     
             }     
         }     
        return $arr;     
    }    

// PHP内置字符串函数实现

//字符串长度
function strlen($str)
{
if ($str == '') return 0;
$count = 0;
while (1){
if ($str[$count] != NULL){
$count++;
continue;
}else{
break;
}
}
return $count;
} 

//截取子串
function substr($str, $start, $length=NULL)
{
if ($str=='' || $start>strlen($str)) return;
if (($length!=NULL) && ($start>0) && ($length>strlen($str)-$start)) return;
if (($length!=NULL) && ($start<0) && ($length>strlen($str)+$start)) return;
if ($length == NULL) $length = (strlen($str) - $start);
if ($start < 0){
for ($i=(strlen($str)+$start); $i<(strlen($str)+$start+$length); $i++) {
$substr .= $str[$i];
}
}
if ($length > 0){
for ($i=$start; $i<($start+$length); $i++) {
$substr .= $str[$i];
}
}
if ($length < 0){
for ($i=$start; $i<(strlen($str)+$length); $i++) {
$substr .= $str[$i];
}
}
return $substr;
}

//字符串翻转
function strrev($str)
{
if ($str == '') return 0;
for ($i=(strlen($str)-1); $i>=0; $i--){
$rev_str .= $str[$i];
}
return $rev_str;
} 

//字符串比较
function strcmp($s1, $s2)
{
if (strlen($s1) < strlen($s2)) return -1;
if (strlen($s1) > strlen($s2)) return 1;
for ($i=0; $i<strlen($s1); $i++){
if ($s1[$i] == $s2[$i]){
continue;
}else{
return false;
}
}
return 0;
} 

//查找字符串
function strstr($str, $substr)
{
$m = strlen($str);
$n = strlen($substr);
if ($m < $n) return false;
for ($i=0; $i<=($m-$n+1); $i++){
$sub = substr($str, $i, $n);
if (strcmp($sub, $substr) == 0) return $i;
}
return false;
} 

//字符串替换
function str_replace($substr, $newsubstr, $str)
{
$m = strlen($str);
$n = strlen($substr);
$x = strlen($newsubstr);
if (strchr($str, $substr) == false) return false;
for ($i=0; $i<=($m-$n+1); $i++){
$i = strchr($str, $substr);
$str = str_delete($str, $i, $n);
$str = str_insert($str, $i, $newstr);
}
return $str;
} 

// 自实现函数

//插入一段字符串
function str_insert($str, $i, $substr)
{
for($j=0; $j<$i; $j++){
$startstr .= $str[$j];
}
for ($j=$i; $j<strlen($str); $j++){
$laststr .= $str[$j];
}
$str = ($startstr . $substr . $laststr);
return $str;
} 

//删除一段字符串
function str_delete($str, $i, $j)
{
for ($c=0; $c<$i; $c++){
$startstr .= $str[$c];
}
for ($c=($i+$j); $c<strlen($str); $c++){
$laststr .= $str[$c];
}
$str = ($startstr . $laststr);
return $str;
} 

//复制字符串
function strcpy($s1, $s2)
{
if (strlen($s1)==NULL || !isset($s2)) return;
for ($i=0; $i<strlen($s1); $i++){
$s2[] = $s1[$i];
}
return $s2;
}

//连接字符串
function strcat($s1, $s2)
{
if (!isset($s1) || !isset($s2)) return;
$newstr = $s1;
for($i=0; $i<count($s); $i++){
$newstr .= $st[$i];
}
return $newsstr;
}

/简单编码函数（与php_decode函数对应）
function php_encode($str)
{
if ($str=='' && strlen($str)>128) return false;
for($i=0; $i<strlen($str); $i++){
$c = ord($str[$i]);
if ($c>31 && $c<107) $c += 20;
if ($c>106 && $c<127) $c -= 75;
$word = chr($c);
$s .= $word;
}
return $s;
}

//简单解码函数（与php_encode函数对应）
function php_decode($str)
{
if ($str=='' && strlen($str)>128) return false;
 
for($i=0; $i<strlen($str); $i++){
$c = ord($word);
if ($c>106 && $c<127) $c = $c-20;
if ($c>31 && $c<107) $c = $c+75;
$word = chr($c);
$s .= $word;
}
return $s;
}

//简单加密函数（与php_decrypt函数对应）
function php_encrypt($str)
{
$encrypt_key = 'abcdefghijklmnopqrstuvwxyz1234567890';
$decrypt_key = 'ngzqtcobmuhelkpdawxfyivrsj2468021359';
if (strlen($str) == 0) return false;
for ($i=0; $i<strlen($str); $i++){
for ($j=0; $j<strlen($encrypt_key); $j++){
if ($str[$i] == $encrypt_key[$j]){
$enstr .= $decrypt_key[$j];
break;
}
}
}
return $enstr;
} 

//简单解密函数（与php_encrypt函数对应）
function php_decrypt($str)
{
$encrypt_key = 'abcdefghijklmnopqrstuvwxyz1234567890';
$decrypt_key = 'ngzqtcobmuhelkpdawxfyivrsj2468021359';
if (strlen($str) == 0) return false;
for ($i=0; $i<strlen($str); $i++){
for ($j=0; $j<strlen($decrypt_key); $j++){
if ($str[$i] == $decrypt_key[$j]){
$enstr .= $encrypt_key[$j];
break;
}
}
}
return $enstr;
}