PHP Common sorting algorithm

Binary lookup must be sequential table  time complexity O (log2n)
function Halfsearch ($arr, $val) {
    $cnt = count ($arr);
    $start = 0;
    $end = $cnt-1;
    while ($start <= $end) {
        $half = Ceil (($start + $end)/2);
        if ($arr [$half] = = $val) {
            return $half;
        }elseif ($arr [$half] > $val) {
            $end = $half-1;
        }elseif ($arr [$half] < $val) {
            $start = $half + 1;
        }
    }
    return-1;

}
$n = Halfsearch ([1,3,6,7,8,9,11,15,17,29,30,31,32,33,34,35,44,41,42,43,44,45,46,50], 30);
Var_dump ($n);

//Order lookup time complexity O (n) 
 function Sortsearch ($arr, $val) {
 $flag = false; 
 $exist =-2;            
 foreach ($arr as $k = + $v) {
 if ($v = = $val) {
 $flag = true; 
 Break    
} 
} 
 
 if ($flag = = False) {
 Return-1; 
    }else{
 return true; 
 } 
} 
 
 $n = Sortsearch ([1,3,6,7,8,9,11,15,17,29,30,31,32,33,34,35,44,41,42,43,44,45,46,50], +); 
 Var_dump ($n); 
 
 
 

///bubble sort time complexity O (n^2) The idea is that a group of numbers (adjacent to two numbers) is compared, if the number is greater than the subsequent exchange, so the result of comparison is to move the largest number to the last position 
 function Maopao ($arr) { 
 $cnt = count ($arr);　　　　　
 for ($i =0; $i <= ($cnt-1); $i + +) {
 $flag = 1; 
             for an array of length N, we need to sort the N-1 wheel, each I-wheel to compare n-i times  
 for ($j =0; $j < ($cnt-$i); $j + +) {
                if ($arr [$j] > $arr [$j +1]) {
 $flag = 0; 
 $tmp = $arr [$j]; 
 $arr [$j] = $arr [$j +1]; 
 $arr [$j +1] = $tmp;        
} 
} 
 if ($flag) {
//proving array order does not require looping 
 break; 
 } 
} 
 return $arr; 
} 
 
 
 $n = Maopao ([1,50,2,6,4,3,8,9,12]); 
 Var_dump ($n); 

The second thought of bubbling, this is not practiced.  
The first round of exchange process: Take the array of the first bit-2 and 5 than, found that no I am small, skip, take-2 and 3 ratio, hair small without my small skip ...
Take-2 and 3 ratio, the hair is smaller than I, two exchange position, the next loop when the first bit of the array has changed, is-3. Well, think about it.
And then the loop is not over, continue to take the first bit of the array (-3), compared with the last 4 of the array, and exchange the next position ...
$numbers = Array ( -2, 5, 3, 1, -3,-4); for ($i =0; $i <count ($numbers); $i + +) {for    ($j = $i +1; $j <count ($numbers); $j + +) {        if ($numbers [$i] > $numbers [$j]) {            $tmp         = $numbers [$i];            $numbers [$i] = $numbers [$j];            $numbers [$j] = $tmp;        }    }    Var_dump ($numbers);} Var_dump ($numbers); exit;

Reference link: http://www.cnblogs.com/shen-hua/p/5422676.html    https://www.cnblogs.com/toxiaonan/archive/2017/11/29/ 7920757.html

PHP Common sorting algorithm