旧文重整理：数据结构和字符串处理代码整理

数据|数据结构|字符串

整理一下以前写的部分算法和字符串处理函数，东西没有什么用，只是为了学习而已。

Author: heiyeluren
Blog: http://blog.csdn.net/heiyeshuwu
Date: 2006-06-10 23:50

<?
//--------------------
// 基本数据结构算法
//--------------------

//二分查找（数组里查找某个元素）
function bin_sch($array, $low, $high, $k){ 
    if ($low <= $high){ 
        $mid = intval(($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 -1; 
} 

//顺序查找（数组里查找某个元素）
function seq_sch($array, $n, $k){ 
    $array[$n] = $k; 
    for($i=0; $i<$n; $i++){ 
        if($array[$i]==$k){ 
            break; 
        } 
    } 
    if ($i<$n){ 
        return $i; 
    }else{ 
        return -1; 
    } 
} 

//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=$count-1; $j>$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 quick_sort($array) {
        if (count($array) <= 1) return $array;

        $key = $array[0];
        $left_arr = array();
        $right_arr = array();

        for ($i=1; $i<count($array); $i++){
                if ($array[$i] <= $key)
                        $left_arr[] = $array[$i];
                else
                        $right_arr[] = $array[$i];
        }

        $left_arr = quick_sort($left_arr);
        $right_arr = quick_sort($right_arr);

        return array_merge($left_arr, array($key), $right_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;
}

//--------------------
// 自实现字符串处理函数
//--------------------

//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;
}

?>