php小算法总结一(数组重排,进制转换,二分查找)

1.两个有序数组组合成一个新的有序数组

<?php
$arr1=array(2,5,7,9,12);
$arr2=array(3,4,6,8,10,11);
function merge_sort($arr1,$arr2){
    $len1=count($arr1);
    $len2=count($arr2);
    $arr=array();
    $i=$j=0;
    while($i<$len1&&$j<$len2){
        if($arr1[$i]<=$arr2[$j]){
            $arr[]=$arr1[$i++];
        }else{
            $arr[]=$arr2[$j++];
        }
    }
    while($i<$len1)
        $arr[]=$arr1[$i++];
    while($j<$len2)
        $arr[]=$arr2[$j++];

    return $arr;
}

print_r(merge_sort($arr1,$arr2));

2.十进制转26进制(a-z表示)

function tento26($num){
    $str='';
    $chu=floor($num/26);
    $yu=$num%26;
    $str.="{".$yu."}";
    if($chu>26){
        $str.=tento26($chu);
    }else{
        $str.="{".$chu."}";
    }
    return $str;
}

function numtoalph($match){
    $alp=' abcdefghijklmnopqrstuvwxyz';
    if($match[1]>=26){
        return false;
    }
    return $alp[$match[1]];
}
$str= tento26(300);

$str1=strrev(preg_replace_callback('#\{(\d+)\}#','numtoalph',$str));
echo $str1;

3.数组转json

<?php
function myjson_encode($arr){
    $jsonstr='{';
    foreach($arr as $k=>$v){
        if(is_array($v)){
            $jsonstr.='"'.$k.'":'.myjson_encode($v).',';
        }else{
            $jsonstr.='"'.$k.'":"'.$v.'",';
        }
    }
    $jsonstr=trim($jsonstr,',');
    $jsonstr.='}';
    return $jsonstr;
}

4.二分查找

<?php
    #二分查找
    function binarySearch(Array $arr, $target) {
        $low = 0;
        $high = count($arr) - 1;

        while($low <= $high) {
            $mid = floor(($low + $high) / 2);
            #找到元素
            if($arr[$mid] == $target) return $mid;
            #中元素比目标大,查找左部
            if($arr[$mid] > $target) $high = $mid - 1;
            #重元素比目标小,查找右部
            if($arr[$mid] < $target) $low = $mid + 1;
        }

        #查找失败
        return false;
    }

    $arr = array(1, 3, 5, 7, 9, 11);
    $inx = binarySearch($arr, 1);
    var_dump($inx);
?>

5.钱币转换

<?php
error_reporting(0);
function cny($ns) {
    static $cnums=array("零","壹","贰","叁","肆","伍","陆","柒","捌","玖"),
    $cnyunits=array("圆","角","分"),
    $grees=array("拾","佰","仟","万","拾","佰","仟","亿");
    list($ns1,$ns2)=explode(".",$ns,2);
    $ns2=array_filter(array($ns2[1],$ns2[0]));

    $ret=array_merge($ns2,array(implode("",_cny_map_unit(str_split($ns1),$grees)),""));
    $ret=implode("",array_reverse(_cny_map_unit($ret,$cnyunits)));
    echo $ret;
    echo "<br>";
    return str_replace(array_keys($cnums),$cnums,$ret);
}
function _cny_map_unit($list,$units) {
    $ul=count($units);
    $xs=array();
    foreach (array_reverse($list) as $x) {
        $l=count($xs);
        if ($x!="0" || !($l%4)){
            $n=($x=='0'?'':$x).($units[($l-1)%$ul]);
        } else{
            $n=is_numeric($xs[0][0])?$x:'';
        }

        array_unshift($xs,$n);
    }
    return $xs;
}

echo cny(2305.32);

2仟3佰05圆3角2分
贰仟叁佰零伍圆叁角贰分

6.约瑟夫环

<?php
function ysf($arr,$current=0,$out=3){
    $count=count($arr);
    $num=1;
    if($count==1){
        echo $arr[0];
    }else{
        while($num++<$out){
            $current++;
            $current=$current%$count;
        }
        echo $arr[$current]."<br>";
        array_splice($arr,$current,1);
        ysf($arr,$current,$out);
    }

}
$arr=[1,2,3,4,5,6,7,8,9,10];
ysf($arr,0,4);