PHP尋找數組中最大值與最小值

<?php     function maxMin(Array $arr) {         $cmpTime = 0;         $count = count($arr);         $big = $small = $arr[0];         for($i = 1; $i < $count; $i++) {             $cmpTime++;             if($big > $arr[$i]) {                 $cmpTime++;                 if($small > $arr[$i]) {                     $small = $arr[$i];                 }              } else {                 $big = $arr[$i];             }         }                  echo "ArrLeng: " . $count . "<br>";         echo "CmpTime: " . $cmpTime . "<br>";         echo "Big: " . $big . "<br>";         echo "Small: " . $small . "<br>";     }          $arr = array(4, 6, 8, 1, 5, 4, 3, 9, 11, 3, 22, 100, 55, 0, 4, -1, 31, 210, -10);     maxMin($arr); ?>

ArrLeng: 19
CmpTime: 29
Big: 210
Small: -10

這個方法是一個不穩定的尋找，找的時候比較是n次，而最壞的時候比較是2n次，下面來看一個穩定的1.5n次比較的方法

<?php     function maxMin(Array $arr) {         $cmpTime = 0;         $count = count($arr);         $biggest = $smallest = $arr[$count - 1];         #每次取出兩個元素，比較兩個元素的大小再與最大值和最小值比較         for($i = 0; $i < $count - 1; $i += 2) {             $cmpTime++;             if($arr[$i] > $arr[$i + 1]) {                $bigger = $arr[$i];                $smaller = $arr[$i + 1];             } else {                $bigger = $arr[$i + 1];                $smaller = $arr[$i];                }             $cmpTime++;                 if($bigger > $biggest) {                 $biggest = $bigger;             }             $cmpTime++;             if($smaller < $smallest) {                $smallest = $smaller;             }         }         echo "ArrLeng: " . $count . "<br>";         echo "CmpTime: " . $cmpTime . "<br>";         echo "Big: " . $biggest . "<br>";         echo "Small: " . $smallest . "<br>";     }          $arr = array(4, 6, 8, 1, 5, 4, 3, 9, 11, 3, 22, 100, 55, 0, 4, -1, 31, 210, -10);     maxMin($arr); ?>

ArrLeng: 19
CmpTime: 27
Big: 210
Small: -10