php数据结构与算法(PHP描述)查找与二分法查找_php技巧

/** 
* 查找 
* 
**/ 
// 顺序查找 
function normal_search($arrData,$val) { 
$len = count($arrData); 
if($len == 0) return -1; 
for($i = 0;$i < $len; $i++ ) { 
echo "find No.",$i + 1," value = ",$arrData[$i]," is = ",$val,"? 
"; 
// 找到了 
if($arrData[$i] == $val) return $i; 
} 
return -1; 
} 

// 测试顺序查找 
$arrData = array(4,51,6,73,2,5,9,33,50,3,4,6,1,4,67); 
echo normal_search($arrData,6),"
"; 
echo normal_search($arrData,66),"
"; 

// 二分法查找(针对有序的列进行查找) 
function binary_search($arrData,$val) { 
$len = count($arrData); 
if($len == 0) return -1; 

$start = 0; 
$end = $len - 1; 

while($start <= $end) { 
$middle = intval(($start + $end)/2); 
echo "start = ",$start," end = ",$end," middle = ",$middle,"
"; 
if($arrData[$middle] == $val) { 
return $middle; 
} elseif ($arrData[$middle] > $val) { 
$end = $middle - 1 ; 
} elseif ($arrData[$middle] < $val) { 
$start = $middle + 1; 
} 
} 
return -1; 
} 

// 测试一下二分法查找 
$arrData = array(1,2,3,4,5,7,8,9,11,23,56,100,104,578,1000); 
echo binary_search($arrData,578),"
"; 
echo binary_search($arrData,66),"
";