PHP有序表查找之插值查找算法示例

<?php
//插值查找(前提是数组必须是有序数组) 事件复杂度　O(logn)
//但对于数组长度比较大，关键字分布又是比较均匀的来说，插值查找的效率比折半查找的效率高
$i = 0; //存储对比的次数
//@param 待查找数组
//@param 待搜索的数字
function insertsearch($arr,$num){
 $count = count($arr);
 $lower = 0;
 $high = $count - 1;
 global $i;
 while($lower <= $high){
  $i ++; //计数器
  if($arr[$lower] == $num){
   return $lower;
  }
  if($arr[$high] == $num){
   return $high;
  }
  // 折半查找  $middle = intval(($lower + $high) / 2);
  $middle = intval($lower + ($num - $arr[$lower]) / ($arr[$high] - $arr[$lower])  ($high - $lower)); 
  if($num < $arr[$middle]){
   $high = $middle - 1;
  }else if($num > $arr[$middle]){
   $lower = $middle + 1;
  }else{
   return $middle;
  }
 }
 return -1;
}
$arr = array(0,1,16,24,35,47,59,62,73,88,99);
$pos = insertsearch($arr,62);
print($pos);
echo "<br>";
echo $i;

$arr = array(0,1,2,2000,2001,2002,2003,2004,5555,69666,99999,100000);
echo "位置".binsearch($arr,5555);
echo "<br>";
echo "比较次数".$i;
$i = 0; //重置比较次数
echo "<br>";
echo "位置".insertsearch($arr,5555);
echo "<br>";
echo "比较次数".$i;

位置8
比较次数2
位置8
比较次数9